Fix itemsoverlay .pro file structure

This patch makes the structure of the pro file of the itemsoverlay
plugin the same as the other plugins (like the mapbox plugin).

Change-Id: Iada6296562282b238c6f793b9f0b80ade8ec6ddf
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

src/plugins/geoservices/itemsoverlay/itemsoverlay.pro

@@ -12,9 +12,10 @@ SOURCES += \
     qgeomappingmanagerengineitemsoverlay.cpp \
     qgeomapitemsoverlay.cpp
 
+OTHER_FILES += \
+    itemsoverlay_plugin.json
+
 PLUGIN_TYPE = geoservices
 PLUGIN_CLASS_NAME = QGeoServiceProviderFactoryItemsOverlay
 load(qt_plugin)
 
-DISTFILES += \
-    itemsoverlay_plugin.json