CVE-2023-28427 fixes leave state unable to sync

Nobody has claimed this yet.

Originally reported at https://github.com/cinnyapp/cinny/issues/1179 as I was unable to repro syncing an element client even after upgrade, but today realized the issue also appears on element, but only if syncing a new element login from scratch.

On Element Web 1.11.35, I see the following trying to sync fresh, which as a result leaves only about 10% of chats loaded and the rest don't receive messages and don't appear in the UI.

```
aught /sync error Error: Unable to encrypt with m.megaolm.v1.aes-sha2
setRoomEncryptionImpl index.ts:2689
onCryptoEvent index.ts:3081
processSyncResponse sync.ts:1431
L utils.ts:425
processSyncResponse sync.ts:1293
doSync sync.ts:915
sync sync.ts:798
startClient client.ts:1515
start MatrixClientPeg.ts:334
me Lifecycle.ts:818
ie Lifecycle.ts:639
te Lifecycle.ts:460
$ Lifecycle.ts:147
loadSession MatrixChat.tsx:496
promise callback*loadSession MatrixChat.tsx:495
Ye MatrixChat.tsx:343
promise callback*Ye MatrixChat.tsx:323
React 13
oe init.tsx:150
async* SecretSharing.ts:185
async* SecretSharing.ts:198
```

Start by reproducing a fresh Element Web login on version 1.11.35 and inspect the sync failure around index.ts, sync.ts, and client.ts named in the stack trace. Done means the m.megaolm.v1.aes-sha2 error no longer stops synchronization and all chats load and receive messages.

Written by the indexing model from the issue text.