fix: Add close() to the AsyncFeatureRequester interface

AsyncPollingUpdateProcessor.stop awaits requester.close(), and the requester param is typed against AsyncFeatureRequester, so the interface must declare close() — otherwise a substitute requester implementing only the interface would fail at shutdown.

Author: jsonbailey

ldclient/interfaces.py

@@ -590,6 +590,13 @@ async def get_all_data(self) -> Mapping[VersionedDataKind, Mapping[str, dict]]:
         """
         ...
 
+    @abstractmethod
+    async def close(self) -> None:
+        """
+        Releases any resources (such as an HTTP transport) owned by the requester.
+        """
+        ...
+
 
 class DiagnosticDescription:
     """