This reverts commit a4595b427d.
Commit a4595b4 avoids sending delivery receipts to rooms that do not contain the
bridge bot. That was necessary as trying to send a read marker would
automatically attempt to join the bridge bot to the room.
That join without invite would fail, hence #483.
But since
https://github.com/mautrix/python/commit/f272f16a1d151a1c6612c9349776eda985c8ea3e
we no longer attempt to join the sender of read receipts, fixing #483 without
necessarily sacrificing the delivery receipt functionality.
Thus:
- a4595b4 is no longer necessary, its original purpose is fulfilled by f272f16.
- a4595b4 prevents delivery receipts from working in unencrypted rooms.
- This reverts a4595b4, thus enabling delivery receipts in unencrypted rooms.
