CVE-2023-28427 fixes leave state unable to sync

[TheBlueMatt]

Originally reported at cinnyapp/cinny#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