swipeTracker: Drop grab-op-begin signal connection

This is	done just to "reset" the gesture when a grab operation
begins.	With grab ops being based on ClutterGrab now, the gesture
will be	implicitly reset when these happen. This is unnecessary	now.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2526>

js/ui/swipeTracker.js

@@ -232,11 +232,6 @@ const TouchSwipeGesture = GObject.registerClass({
 
         this._allowedModes = allowedModes;
         this._distance = global.screen_height;
-
-        global.display.connect('grab-op-begin', () => {
-            this.cancel();
-        });
-
         this._lastPosition = 0;
     }