Update vlc-android/res/xml/shortcuts.xml to fix a build error

I get this error when I'm running gradle build tasks.

> Task :vlc-android:processReleaseResources FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':vlc-android:processReleaseResources'.
> A failure occurred while executing com.android.build.gradle.internal.tasks.Workers$ActionFacade
   > Android resource linking failed
     /home/videolan/vlc-android/vlc-android/res/layout/file_picker_fragment.xml:16: AAPT: warn: generated id 'android:id/empty' for external package 'android'.

     /home/videolan/vlc-android/vlc-android/res/xml/shortcuts.xml:5: AAPT: error: resource string/resume_playback_long (aka org.videolan.vlc:string/resume_playback_long) not found.

     /home/videolan/vlc-android/vlc-android/res/xml/shortcuts.xml:5: AAPT: error: resource string/resume_playback_short (aka org.videolan.vlc:string/resume_playback_short) not found.