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

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https://hg.mozilla.org/integration/gaia-central/rev/c831d6b0e27a
Author: punamdahiya <punamdahiya@yahoo.com>
Desc: Merge pull request #14542 from punamdahiya/Bug947028

Bug 947028 - Fix of overlapping checkboxes while selecting ring tones r=davidflanagan

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https://hg.mozilla.org/integration/gaia-central/rev/c299cbf08edc
Author: Punam Dahiya <punamdahiya@yahoo.com>
Desc: Bug 947028 - Fix of overlapping checkboxes while selecting ring tones r=davidflanagan