Fix wrong handling of encrypted rooms when loading them from sync accumulator (#3640)
* Revert "Ensure we don't overinflate the total notification count (#3634)"
This reverts commit fd0c4a7f5697b33020362de72d19521c22efd63b.
* Fix wrong handling of encrypted rooms when loading them from sync accumulator
* Tidy up code, removing sections which didn't make any difference
* Add test