Drop layout-Allow-updating-struts-in-Overview.patch

Because it caused a regression LP: #1922772 and doesn't seem to have
been necessary anyway. Because:

 * The patch incorrectly suggests it fixes LP: #1727225, which is both
   low priority and apparently false. The fix for that bug will come
   in mutter 40 only. Not from gnome-shell.

 * The commit 9c123477 message suggests it fixes #1917939, which is
   lower priority than LP: #1922772 and apparently false. The fix for that
   bug (mutter#1627) is in mutter only (mutter!1755).

So the patch being removed doesn't seem to do anything useful other than
cause a new regression LP: #1922772. Remove it.

LP: #1922772