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

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https://hg.mozilla.org/integration/gaia-central/rev/c51a7687c52f
Author: Rudy Lu <me@rudy.lu>
Desc: Merge pull request #16106 from flodolo/bug969978

Bug 969978 - Improve Italian keyboard layout (alternative chars for 'e' and '.')
r=rudylu

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https://hg.mozilla.org/integration/gaia-central/rev/60f3c755d5c9
Author: Francesco Lodolo (:flod) <flod@lodolo.net>
Desc: Bug 969978 - Improve Italian keyboard layout (alternates for 'e' and '.')

* Invert é and è, since the latter is much more frequent.
* Add apostrophe and question/exclamation mark to “.”
Bumping manifests a=b2g-bump