Clear telemetry client cache in e2e test teardown

Added _clients.clear() to the teardown fixture to prevent telemetry
clients from persisting across e2e tests, which was causing session ID
pollution in test_concurrent_queries_sends_telemetry.

Author: samikshya-db

tests/e2e/test_concurrent_telemetry.py

@@ -41,6 +41,7 @@ def telemetry_setup_teardown(self):
                 TelemetryClientFactory._executor.shutdown(wait=True)
                 TelemetryClientFactory._executor = None
             TelemetryClientFactory._stop_flush_thread()
+            TelemetryClientFactory._clients.clear()
             TelemetryClientFactory._initialized = False
 
     def test_concurrent_queries_sends_telemetry(self):