iOS: Don't import MainViewController.h in PluginUtil.h

- Fixes warning: It is unsafe to rely on the MainViewController class as an extension point. Update your code to extend CDVViewController instead. This code will stop working in Cordova iOS 9!

Author: GitToTheHub

src/ios/GoogleMaps/PluginUtil.h

@@ -8,7 +8,6 @@
 
 #import <Foundation/Foundation.h>
 #import <Cordova/CDV.h>
-#import "MainViewController.h"
 #import <QuartzCore/QuartzCore.h>
 #import <objc/runtime.h>
 //#import "MFGoogleMapAdditions/GMSCoordinateBounds+Geometry.h"