Update annotation for client.execute_batch, get_execution_result argu… (#483)

Co-authored-by: Hanusz Leszek <[email protected]>

Author: rahul-gj

gql/client.py

@@ -251,7 +251,7 @@ def execute_batch_sync(
         *,
         serialize_variables: Optional[bool] = None,
         parse_result: Optional[bool] = None,
-        get_execution_result: Literal[False],
+        get_execution_result: Literal[False] = ...,
         **kwargs,
     ) -> List[Dict[str, Any]]:
         ...  # pragma: no cover
@@ -487,7 +487,7 @@ def execute_batch(
         *,
         serialize_variables: Optional[bool] = None,
         parse_result: Optional[bool] = None,
-        get_execution_result: Literal[False],
+        get_execution_result: Literal[False] = ...,
         **kwargs,
     ) -> List[Dict[str, Any]]:
         ...  # pragma: no cover
@@ -1096,7 +1096,7 @@ def execute_batch(
         *,
         serialize_variables: Optional[bool] = None,
         parse_result: Optional[bool] = None,
-        get_execution_result: Literal[False],
+        get_execution_result: Literal[False] = ...,
         **kwargs,
     ) -> List[Dict[str, Any]]:
         ...  # pragma: no cover