fix(api): idle gripper should idle (#13558)

* wrong logic

api/src/opentrons/hardware_control/instruments/ot3/gripper_handler.py

@@ -139,13 +139,13 @@ def check_ready_for_jaw_move(self) -> None:
             raise GripError("Gripper jaw must be homed before moving")
 
     def is_ready_for_idle(self) -> bool:
-        """Raise an exception if it is not currently valid to idle the jaw."""
+        """Gripper can idle when the jaw is not currently gripping."""
         gripper = self.get_gripper()
         if gripper.state == GripperJawState.UNHOMED:
             self._log.warning(
                 "Gripper jaw is not homed and cannot move to idle position."
             )
-        return gripper.state == GripperJawState.GRIPPING
+        return gripper.state != GripperJawState.GRIPPING
 
     def is_ready_for_jaw_home(self) -> bool:
         """Raise an exception if it is not currently valid to home the jaw."""