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

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https://hg.mozilla.org/integration/gaia-central/rev/b43fa272b6a2
Author: Jared Hirsch <ohai@6a68.net>
Desc: Merge pull request #17613 from 6a68/bug-987418-fxa-system-app-copy-update

Bug 987418 - Update copy in fxa system app

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https://hg.mozilla.org/integration/gaia-central/rev/7bd5bd188d26
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 987418 - Update copy in fxa system app r=ferjm

  Also reverts commit 2c7d550 (bug 961009) and renames locales file per
  comment 1 in that bug.
Bumping manifests a=b2g-bump