Merge pull request 'matrix: set forgotten_room_retention_period to 7d' (#124) from matrix/room-retention-period into main

Reviewed-on: #124
Reviewed-by: Hendrik Sokolowski <hensoko@noreply.git.pub.solar>
Reviewed-by: teutat3s <teutat3s@noreply.git.pub.solar>

hosts/nachtigall/apps/matrix/synapse.nix

@@ -188,6 +188,7 @@ in
         per_second = 0.17;
       };
       redaction_retention_period = "7d";
+      forgotten_room_retention_period = "7d";
       redis.enabled = false;
       registration_requires_token = false;
       registrations_require_3pid = [ "email" ];