Addressing deprecation warnings for firestore query syntax

Author: ScottMansfield

src/google/adk/integrations/firestore/firestore_memory_service.py

@@ -22,6 +22,7 @@
 from typing import Optional
 from typing import TYPE_CHECKING
 
+from google.cloud.firestore_v1.base_query import FieldFilter
 from typing_extensions import override
 
 from ...events.event import Event
@@ -289,9 +290,9 @@ async def _search_by_keyword(
     """Searches for events matching a single keyword."""
     query = (
         self.client.collection_group(self.events_collection)
-        .where("appName", "==", app_name)
-        .where("userId", "==", user_id)
-        .where("keywords", "array_contains", keyword)
+        .where(filter=FieldFilter("appName", "==", app_name))
+        .where(filter=FieldFilter("userId", "==", user_id))
+        .where(filter=FieldFilter("keywords", "array_contains", keyword))
     )
 
     docs = await query.get()