fix: Add missing files_api parameter to MemoryToolRuntimeImpl test (#3394)

# What does this PR do?
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relevant issues if applicable. -->
The test_query_adds_vector_db_id_to_chunk_metadata test was failing
because MemoryToolRuntimeImpl.__init__() now requires a files_api
parameter.

Fixes failing unit tests for Python 3.12 and 3.13.

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## Test Plan
<!-- Describe the tests you ran to verify your changes with result
summaries. *Provide clear instructions so the plan can be easily
re-executed.* -->

tests/unit/rag/test_rag_query.py

@@ -88,6 +88,7 @@ class TestRagQuery:
             config=MagicMock(),
             vector_io_api=MagicMock(),
             inference_api=MagicMock(),
+            files_api=MagicMock(),
         )
 
         vector_db_ids = ["db1", "db2"]