unblacklist some tests (#8474)

It seems most of these blacklisted tests do actually pass most of the time.

I'm of the opinion that having them blacklisted here means there is very little incentive for us to deflake any flaky tests, and meanwhile any value in those tests is completely lost.

.buildkite/worker-blacklist

 # This file serves as a blacklist for SyTest tests that we expect will fail in
 # Synapse when run under worker mode. For more details, see sytest-blacklist.
 
-Message history can be paginated
-
 Can re-join room if re-invited
 
-The only membership state included in an initial sync is for all the senders in the timeline
-
-Local device key changes get to remote servers
-
-If remote user leaves room we no longer receive device updates
-
-Forgotten room messages cannot be paginated
-
-Inbound federation can get public room list
-
-Members from the gap are included in gappy incr LL sync
-
-Leaves are present in non-gapped incremental syncs
-
-Old leaves are present in gapped incremental syncs
-
-User sees updates to presence from other users in the incremental sync.
-
-Gapped incremental syncs include all state changes
-
-Old members are included in gappy incr LL sync if they start speaking
-
 # new failures as of https://github.com/matrix-org/sytest/pull/732
 Device list doesn't change if remote server is down
-Remote servers cannot set power levels in rooms without existing powerlevels
-Remote servers should reject attempts by non-creators to set the power levels
 
 # https://buildkite.com/matrix-dot-org/synapse/builds/6134#6f67bf47-e234-474d-80e8-c6e1868b15c5
 Server correctly handles incoming m.device_list_update
-
-# this fails reliably with a torture level of 100 due to https://github.com/matrix-org/synapse/issues/6536
-Outbound federation requests missing prev_events and then asks for /state_ids and resolves the state
-
-Can get rooms/{roomId}/members at a given point

changelog.d/8474.misc

+Unblacklist some sytests.

sytest-blacklist

@@ -34,9 +34,6 @@ New federated private chats get full presence information (SYN-115)
 # this requirement from the spec
 Inbound federation of state requires event_id as a mandatory paramater
 
-# Blacklisted until https://github.com/matrix-org/synapse/pull/6486 lands
-Can upload self-signing keys
-
 # Blacklisted until MSC2753 is implemented
 Local users can peek into world_readable rooms by room ID
 We can't peek into rooms with shared history_visibility