[mac] Add NSScrollView.WillStartLiveScrollNotification (#8205)

- https://github.com/xamarin/xamarin-macios/issues/7712

src/appkit.cs

@@ -13466,6 +13466,9 @@ namespace AppKit {
 
 		[Notification, Field ("NSScrollViewDidEndLiveMagnifyNotification")]
 		NSString DidEndLiveMagnifyNotification { get; }
+		
+		[Notification, Field ("NSScrollViewWillStartLiveScrollNotification")]
+		NSString WillStartLiveScrollNotification { get; }
 
 		[Mac (10,9), Notification, Field ("NSScrollViewDidLiveScrollNotification")]
 		NSString DidLiveScrollNotification { get; }

tests/xtro-sharpie/macOS-AppKit.ignore

@@ -442,7 +442,6 @@
 !missing-field! NSRuleEditorPredicateOperatorType not bound
 !missing-field! NSRuleEditorPredicateOptions not bound
 !missing-field! NSRuleEditorPredicateRightExpression not bound
-!missing-field! NSScrollViewWillStartLiveScrollNotification not bound
 !missing-field! NSSelectedIdentifierBinding not bound
 !missing-field! NSSelectedIndexBinding not bound
 !missing-field! NSSelectedLabelBinding not bound