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

========

https://hg.mozilla.org/integration/gaia-central/rev/a4853a0d6cdf
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #23946 from RudyLu/keyboard/Bug1065961

Bug 1065961 - Sometimes the last alternative key would be wrongly highlighted.
r=timdream

========

https://hg.mozilla.org/integration/gaia-central/rev/dd8924b75e70
Author: Rudy Lu <me@rudy.lu>
Desc:  Bug 1065961 - Sometimes the last alternative key would be wrongly
 highlighted.
  - use math to calculate the transfered menu target.
  - move the main calculation into MenuView's getMenuTarget.
Bumping manifests a=b2g-bump