Bumping gaia.json for 2 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/f48f21472127
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #10876 from jrburke/bug891728-image-attach-module

Bug 891728 [email] dynamic require of shared/mime_mapper fails due to rel-path r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/541dda1c48c7
Author: jrburke <jrburke@gmail.com>
Desc: Bug 891728 [email] dynamic require of shared/mime_mapper fails due to rel-path