Bumping gaia.json for 1 gaia-central revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/a8e6d298564a
Author: John Ford <john@johnford.info>
Desc: Revert "Merge pull request #14632 from alivedise/bugzilla/948596_v2/activity-window-size-copy"

This reverts commit 888f9df5515a47d2f5806efee77485e05e1e5416, reversing
changes made to 53b010647062b4e2637f98ac3538af1c7bfe723a.

This was backed out because of https://bugzilla.mozilla.org/show_bug.cgi?id=950136#c11

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "a8720a418a856aa3d51263eee70fc40df28ad9b2", 
+    "revision": "a8e6d298564ac14c79d23ab170be2599f8ae9678", 
     "repo_path": "/integration/gaia-central"
 }