Threads: removed "unread_thread_notifications" from sync filters for server that doesn't support MSC3773

- Update after review

Riot/Modules/MatrixKit/Models/Account/MXKAccount.h

@@ -359,11 +359,6 @@ typedef BOOL (^MXKAccountOnCertificateChange)(MXKAccount *mxAccount, NSData *cer
 - (void)resetDeviceId;
 
 #pragma mark - Sync filter
-/**
- Check if the homeserver supports room members lazy loading.
- @param completion the check result.
- */
-- (void)supportLazyLoadOfRoomMembers:(void (^)(BOOL supportLazyLoadOfRoomMembers))completion;
 
 /**
  Call this method at an appropriate time to attempt dehydrating to a new backup device