End on exit is already the default expected behavior

synapse/http/client.py

@@ -413,7 +413,6 @@ class SimpleHttpClient:
                 SpanAttributes.HTTP_METHOD: method,
                 SpanAttributes.HTTP_URL: uri,
             },
-            end_on_exit=True,
         ):
             try:
                 body_producer = None

synapse/http/matrixfederationclient.py

@@ -528,7 +528,6 @@ class MatrixFederationHttpClient:
                 SpanAttributes.HTTP_METHOD: request.method,
                 SpanAttributes.HTTP_URL: request.path,
             },
-            end_on_exit=True,
         )
 
         # Inject the span into the headers