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

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https://hg.mozilla.org/integration/gaia-central/rev/622362e38615
Author: Jared Hirsch <ohai@6a68.net>
Desc: Merge pull request #17611 from 6a68/bug-987417-fxa-settings-copy-update

Bug 987417 - Update copy in firefox accounts settings app

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https://hg.mozilla.org/integration/gaia-central/rev/6887ed12d1b2
Author: Jared Hirsch <ohai@6a68.net>
Desc: Bug 987417 - Update copy in firefox accounts settings app r=arthurcc
Bumping manifests a=b2g-bump