Remove testAll task
Remove testAll task

The testAll Gradle task hasn't been properly supported since allowing
Android instrumentation tests in release build types. It's unused in CI
too so it's appropriate to remove.

Change-Id: Idac5284624513d2f51fb1044f322601bf3a0310f

wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,wikimedia/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,dbrant/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,dbrant/apps-android-wikipedia,anirudh24seven/apps-android-wikipedia,wikimedia/apps-android-wikipedia,dbrant/apps-android-wikipedia,dbrant/apps-android-wikipedia,SAGROUP2/apps-android-wikipedia,wikimedia/apps-android-wikipedia