Recurring too large event from matrix.kiwifarms.net

This issue has been migrated from [#6782](https://github.com/matrix-org/synapse/issues/6782).

---

### Description

I've been getting the following in my logs for the past few hours repeatedly:

```
2020-01-25 16:43:56,039 - synapse.http.matrixfederationclient - 164 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net- {GET-O-120740} [matrix.kiwifarms.net] Completed: 200 OK
2020-01-25 16:43:56,113 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$15799662694FdIUz:calamari.space- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,114 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996628079659VsCoS:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,115 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996627879658ekygD:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,116 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996622079636ipUVL:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,117 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996627579656cgFdh:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,117 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,118 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996628179660apjeR:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,121 - synapse.handlers.federation - 2249 - INFO - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net-$157996628479661YFIAM:matrix.kiwifarms.net-$157996626879651nsxTJ:matrix.kiwifarms.net- Skipping auth_event fetch for outlier
2020-01-25 16:43:56,121 - synapse.handlers.federation - 411 - WARNING - PUT-804886-$157996629879666qwvGV:matrix.kiwifarms.net-$157996628879662OVzrF:matrix.kiwifarms.net- [!PvQGNjiCNulFZsMPud:matrix.org $157996628879662OVzrF:matrix.kiwifarms.net] Error attempting to resolve state at missing prev_events
...
Traceback (most recent call last):
File "/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py", line 372, in on_receive_pdu
origin, room_id, p, include_event_in_state=True
File "/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py", line 587, in _get_state_for_room
destination, room_id, desired_events
File "/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py", line 640, in _get_events_from_store_or_dest
destination=destination, room_id=room_id, events=missing_events
File "/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py", line 1106, in _get_events_and_persist
destination, event_infos,
File "/home/synapse/synapse/env/lib/python3.7/site-packages/twisted/internet/defer.py", line 749, in send
raise result.value
twisted.internet.defer.FirstError: FirstError[#6, [Failure instance: Traceback: : 413: event too large
/home/synapse/synapse/env/lib/python3.7/site-packages/twisted/internet/defer.py:1418:_inlineCallbacks
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py:1948:_prep_event
/home/synapse/synapse/env/lib/python3.7/site-packages/twisted/internet/defer.py:1613:unwindGenerator
/home/synapse/synapse/env/lib/python3.7/site-packages/twisted/internet/defer.py:1529:_cancellableInlineCallbacks
--- ---
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py:1793:prep
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py:1948:_prep_event
/home/synapse/synapse/env/lib/python3.7/site-packages/twisted/internet/defer.py:1418:_inlineCallbacks
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/handlers/federation.py:2140:do_auth
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/event_auth.py:49:check
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/event_auth.py:183:_check_size_limits
/home/synapse/synapse/env/lib/python3.7/site-packages/synapse/event_auth.py:170:too_big
]]
```

It seems to be affecting the performance of my server a bit.

Synapse v1.9.0