fix(BA-5837): drop unused type:ignore from gql_mutation decorators

`@gql_mutation(...)` doesn't trigger the `[misc]` complaint these
ignores were guarding against any longer (mypy now reports
`[unused-ignore]`). Strip the comments on the three admin bulk
mutation resolvers so typecheck is clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jopemachine

src/ai/backend/manager/api/gql/app_config_fragment/resolver/mutation.py

@@ -35,7 +35,7 @@
             "and failures are collected per-item (admin only)."
         ),
     )
-)  # type: ignore[misc]
+)
 async def admin_bulk_create_app_config_fragments(
     info: Info[StrawberryGQLContext],
     input: AdminBulkCreateAppConfigFragmentInputGQL,
@@ -53,7 +53,7 @@ async def admin_bulk_create_app_config_fragments(
             "(admin only)."
         ),
     )
-)  # type: ignore[misc]
+)
 async def admin_bulk_update_app_config_fragments(
     info: Info[StrawberryGQLContext],
     input: AdminBulkUpdateAppConfigFragmentInputGQL,
@@ -68,7 +68,7 @@ async def admin_bulk_update_app_config_fragments(
         added_version=NEXT_RELEASE_VERSION,
         description="Cleanup-only deletion; absent keys are no-oped (admin only).",
     )
-)  # type: ignore[misc]
+)
 async def admin_bulk_purge_app_config_fragments(
     info: Info[StrawberryGQLContext],
     input: AdminBulkPurgeAppConfigFragmentInputGQL,