fix: minor type annotation error

Author: achimnol

src/ai/backend/client/func/storage.py

@@ -67,7 +67,7 @@ async def detail(
         cls,
         vfolder_host: str,
         fields: Sequence[str] = _default_detail_fields,
-    ) -> Sequence[dict]:
+    ) -> dict:
         query = textwrap.dedent("""\
             query($vfolder_host: String!) {
                 storage_volume(id: $vfolder_host) {$fields}