Replace SlavedKeyStore with a shim

since we're pulling everything out of KeyStore anyway, we may as well simplify
it.

synapse/replication/slave/storage/keys.py

@@ -13,19 +13,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from synapse.storage import DataStore
-from synapse.storage.keys import KeyStore
+from synapse.storage import KeyStore
 
-from ._base import BaseSlavedStore, __func__
+# KeyStore isn't really safe to use from a worker, but for now we do so and hope that
+# the races it creates aren't too bad.
 
-
-class SlavedKeyStore(BaseSlavedStore):
-    _get_server_verify_key = KeyStore.__dict__[
-        "_get_server_verify_key"
-    ]
-
-    get_server_verify_keys = __func__(DataStore.get_server_verify_keys)
-    store_server_verify_key = __func__(DataStore.store_server_verify_key)
-
-    get_server_keys_json = __func__(DataStore.get_server_keys_json)
-    store_server_keys_json = __func__(DataStore.store_server_keys_json)
+SlavedKeyStore = KeyStore