fix(BA-5584): remove __version__ reference from openid webapp

The openid plugin's webapp.py still imported __version__ which was
removed in the previous commit. This caused CI typecheck and component
test failures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: fregataa

src/ai/backend/manager/plugin/openid/webapp.py

@@ -33,7 +33,6 @@
 from ai.backend.manager.models.utils import ExtendedAsyncSAEngine
 from ai.backend.manager.plugin.webapp import WebappPlugin
 
-from . import __version__
 from .valkey_client import ValkeyOpenIDClient
 
 log = BraceStyleAdapter(logging.getLogger(__name__))
@@ -46,7 +45,7 @@ class OpenIDError(Exception):
 
 
 async def ping(_request: web.Request) -> web.Response:
-    return web.Response(status=200, body=f"Backend.AI OpenID Connect SSO plugin ({__version__}).")
+    return web.Response(status=200, body="Backend.AI OpenID Connect SSO plugin.")
 
 
 def generate_random_string(length: int = 10) -> str: