Remove unnecessary pass statements. (#12206)

changelog.d/12206.misc

synapse/handlers/device.py

synapse/handlers/presence.py

synapse/http/matrixfederationclient.py

synapse/http/server.py

synapse/rest/media/v1/_base.py

synapse/server.py

synapse/storage/databases/main/registration.py

synapse/storage/schema/main/delta/30/as_users.py

synapse/util/caches/treecache.py

tests/handlers/test_password_providers.py