title: Validate XML gives Error:External resource http://schemas.android.com/apk/res/android is not registered
body: <p>I have reinstalled Android Studio (Arctic Fox 2020.3.1 Patch 3).</p>
  <p>Any xml file I right click and choose Validate on gives the error: Error:External resource <a href="http://schemas.android.com/apk/res/android" rel="nofollow noreferrer">http://schemas.android.com/apk/res/android</a> is not registered</p>
  <p>I can start a new project and do the same and get the same error. So seems either a bug in AS or something bad in my environment managed to survive the reinstall. (Tested on two windows computers)</p>
  <p>I can run projects w/o problems it's just AS claiming there's a problem.</p>
  <p>Any idea what could cause this (or confirm its an AS bug)?</p>