Rename errors.py -> error.py

anonstream/routes/__init__.py

@@ -1,7 +1,7 @@
 # SPDX-FileCopyrightText: 2022 n9k <https://git.076.ne.jp/ninya9k>
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
-import anonstream.routes.errors
+import anonstream.routes.error
 import anonstream.routes.core
 import anonstream.routes.websocket
 import anonstream.routes.nojs