Make GridPropertyEditor dirty if a control is removed

This is the same fix that @inetzo made for a PR I checked earlier today except the fix was for U8.  Since I didn't notice it was U8 until I had merged, I thought I'd fix it here but credit should go to @inetzo 

#12097

Author: OwainWilliams

src/Umbraco.Web.UI.Client/src/views/propertyeditors/grid/grid.controller.js

@@ -667,6 +667,7 @@ angular.module("umbraco")
             $scope.removeControl = function (cell, $index) {
                 $scope.currentControl = null;
                 cell.controls.splice($index, 1);
+                currentForm.$setDirty();
             };
 
             $scope.percentage = function (spans) {