Fix event auth for knocking

[S7evinK]

Knocking is not allowed in restricted rooms.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (19c0a71) 59.80% compared to head (fbff586) 60.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #431      +/-   ##
==========================================
+ Coverage   59.80%   60.03%   +0.23%     
==========================================
  Files          51       51              
  Lines        7137     7134       -3     
==========================================
+ Hits         4268     4283      +15     
+ Misses       2477     2458      -19     
- Partials      392      393       +1     

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[kegsay]

Seems really broken that we allow invite->knock transitions... Invites are more important than knocks as you can then transition to join from it, but you can't with knock.

The only time I guess it's useful is to revoke an invite of a knocked user, but I would have probably advocated for invite->leave and then make the knocker knock again, but oh well.

Codewise LGTM