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

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https://hg.mozilla.org/integration/gaia-central/rev/2fff3999b2f7
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Merge pull request #20874 from dominickuo/bug-1026328

Bug 1026328 - [Settings] Also set the l10nId to the tone buttons, r=EragonJ

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https://hg.mozilla.org/integration/gaia-central/rev/871c33749da5
Author: Dominic Kuo <dkuo@mozilla.com>
Desc: Bug 1026328 - [Settings] Also set the l10nId to the tone buttons
Bumping manifests a=b2g-bump