Use full GitHub links instead of bare issue numbers. (#16637)

.git-blame-ignore-revs

changelog.d/16637.misc

debian/changelog

pyproject.toml

synapse/app/generic_worker.py

synapse/federation/sender/__init__.py

synapse/handlers/federation_event.py

synapse/handlers/presence.py

synapse/handlers/sync.py

synapse/handlers/user_directory.py

synapse/http/matrixfederationclient.py

...module_api/callbacks/third_party_event_rules_callbacks.py

synapse/storage/databases/__init__.py

synapse/storage/databases/main/events_bg_updates.py

synapse/storage/databases/main/events_worker.py

synapse/storage/databases/main/monthly_active_users.py

synapse/storage/databases/main/purge_events.py

synapse/storage/engines/postgres.py

synapse/storage/schema/__init__.py

...orage/schema/main/delta/54/delete_forward_extremities.sql