Update annotation for client.execute_batch, get_execution_result argu…

…ment.

client.execute_batch  was showing "No overload for provided arguments" in Pylance for vscode. Had to provide argument for get_execution_result to suppress error. Update overloads to have default values to overcome this.

gql/client.py

@@ -498,7 +498,7 @@ def execute_batch(
         *,
         serialize_variables: Optional[bool] = None,
         parse_result: Optional[bool] = None,
-        get_execution_result: Literal[False],
+        get_execution_result: Literal[False] = False,
         **kwargs,
     ) -> List[Dict[str, Any]]:
         ...  # pragma: no cover
@@ -510,7 +510,7 @@ def execute_batch(
         *,
         serialize_variables: Optional[bool] = None,
         parse_result: Optional[bool] = None,
-        get_execution_result: Literal[True],
+        get_execution_result: Literal[True] = True,
         **kwargs,
     ) -> List[ExecutionResult]:
         ...  # pragma: no cover