fix private version (the issue remain in sdl2 bootstrap)

Author: tito

pythonforandroid/bootstraps/sdl2_gradle/build/templates/strings.tmpl.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
     <string name="app_name">{{ args.name }}</string>
-    <string name="private_version">0.1</string>
+    <string name="private_version">{{ private_version }}</string>
     <string name="presplash_color">{{ args.presplash_color }}</string>
     <string name="urlScheme">{{ url_scheme }}</string>
 </resources>