Receiving invites from blocked users

### Description

Imagine the following scenario:

- user A creates room R1
- user A invites user B in room R1
- user B receives a pushed notification from user A
- user B declines and blocks user A
- user A creates room R2
- user A invites user B in room R2
- user B receives a pushed notification from user A

I guess this is wrong. user B should not receive a pushed notification from user A if user B has been blocked by user A.

The Matrix Rust SDK is trying to prevent that with https://github.com/matrix-org/matrix-rust-sdk/pull/5081, but I suspect the homeserver should also filter that out.

Is it a spec issue? Is it a homeserver missing feature? A regression? A client-side problem only? Thoughts?

### Steps to reproduce

See my previous scenario above.

### Homeserver

matrix.org

### Synapse Version

1.130.0 (b=matrix-org-hotfixes-priv,f6cffa1b29)

### Installation Method

I don't know

### Database

-

### Workers

Single process

### Platform

-

### Configuration

-

### Relevant log output

```shell
-
```

### Anything else that would be useful to know?

-

No Synapse file, test, or entry point is named. Start by comparing the reported behavior with the Matrix specification and matrix-rust-sdk PR 5081, then trace how Synapse handles room invitations and pushed notifications. Done means identifying whether filtering belongs in the homeserver, client, or specification and documenting the expected behavior.

Written by the indexing model from the issue text.