Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/b71a21eeff88
Author: Yura Zenevich <yura.zenevich@gmail.com>
Desc: Merge pull request #19561 from yzen/bug-1014761

Bug 1014761 - improved the way utility tray visibility works with the sc...

========

https://hg.mozilla.org/integration/gaia-central/rev/7166d2cf212a
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 1014761 - improved the way utility tray visibility works with the screen reader.

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "32908f407ce43eb091aa683bce444fd52df01f6f", 
+    "revision": "b71a21eeff8804d08af63bd4e652cabb65e25443", 
     "repo_path": "/integration/gaia-central"
 }