Fix link to PermissionHandlerEnums.h (#803)

permission_handler/README.md

@@ -77,7 +77,7 @@ You must list permission you want to use in your application :
          # ## dart: PermissionGroup.camera
          # 'PERMISSION_CAMERA=1'
          #
-         #  Preprocessor definitions can be found in: https://github.com/Baseflow/flutter-permission-handler/blob/master/permission_handler/ios/Classes/PermissionHandlerEnums.h
+         #  Preprocessor definitions can be found in: https://github.com/Baseflow/flutter-permission-handler/blob/master/permission_handler_apple/ios/Classes/PermissionHandlerEnums.h
          config.build_settings['GCC_PREPROCESSOR_DEFINITIONS'] ||= [
            '$(inherited)',