fix: query param docs

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Author: sangeethailango

plane/models/query_params.py

@@ -114,9 +114,9 @@ class WorkItemCountQueryParams(BaseModel):
     Accepts the same ``filters`` and ``pql`` as :class:`WorkItemQueryParams`
     plus an optional ``group_by`` field.
 
-    Without ``group_by`` the response is ``{"count": N}``.
+    Without ``group_by`` the response is ``{"grouped_by": null, "sub_grouped_by": null, "total_count": N, "grouped_counts": {}}``.
     With ``group_by`` the response is
-    ``{"grouped_by": ..., "total_count": N, "results": {group_key: {"count": N}}}``.
+    ``{"grouped_by": ..., "sub_grouped_by": null, "total_count": N, "grouped_counts": {group_key: {"count": N}}}``.
     """
 
     model_config = ConfigDict(extra="ignore", populate_by_name=True)