fix: resolve pyright type check errors in LangChain callback handler

- Suppress reportUnknownArgumentType/reportUnknownVariableType on
  serialized_id list join (type comes from untyped dict[str, Any])
- Remove unnecessary isinstance(query, str) check — query param is
  already typed as str in on_retriever_start signature

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: nagkumar91

instrumentation-genai/opentelemetry-instrumentation-langchain/src/opentelemetry/instrumentation/langchain/callback_handler.py

@@ -115,7 +115,7 @@ def _resolve_retriever_store_id(
             return serialized_id
         if isinstance(serialized_id, list) and serialized_id:
             try:
-                return ".".join(str(part) for part in serialized_id)
+                return ".".join(str(part) for part in serialized_id)  # type: ignore[reportUnknownArgumentType, reportUnknownVariableType]
             except TypeError:
                 return None
         return None
@@ -398,11 +398,7 @@ def on_retriever_start(
             attributes[GEN_AI_MEMORY_STORE_NAME] = store_name
         if store_id := self._resolve_retriever_store_id(serialized, metadata):
             attributes[GEN_AI_MEMORY_STORE_ID] = store_id
-        if (
-            query
-            and self._should_capture_memory_query()
-            and isinstance(query, str)
-        ):
+        if query and self._should_capture_memory_query():
             attributes[GEN_AI_MEMORY_QUERY] = query
         if metadata and metadata.get("memory_namespace"):
             attributes[GEN_AI_MEMORY_NAMESPACE] = metadata["memory_namespace"]