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

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https://hg.mozilla.org/integration/gaia-central/rev/2303ad586dc1
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #23851 from RudyLu/keyboard/Bug1062105

Bug 1062105 - [Keyboard] Alternate keys list overflows needs UI improvement.
r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/6c518b019344
Author: Rudy Lu <me@rudy.lu>
Desc:  Bug 1062105 - [Keyboard] Alternate keys list overflows needs UI
 improvement.
  - Add border to multi-row alternatives char menu.
  - Adjust the positioning of the menu to align with the key row
    underneath.
Bumping manifests a=b2g-bump