Solved the bug related to the toggle inspector of iOS

Summary:
Before this diff the nodes were not invalidated properly when the new view got added in the hierarchy, due to this there was following bug.

https://our.intern.facebook.com/intern/px/p/15RSP

Reviewed By: Andrey-Mishanin

Differential Revision: D21285438

fbshipit-source-id: b72aa93856688b31296ae1df4f15e128037aa1ca

iOS/Plugins/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin/FlipperKitLayoutPlugin.mm

@@ -371,6 +371,10 @@
       });
 }
 
+- (void)invalidateRootNode {
+  [self invalidateNode:_rootNode];
+}
+
 - (void)_reportInvalidatedObjects {
   NSMutableArray* nodes = [NSMutableArray new];
   { // scope mutex acquisition