Bumping gaia.json for 3 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/7780ee967fbd
Author: Ben Francis <ben@tola.me.uk>
Desc: Bug 914040 - BrowserDB gaia unit tests failing in TBPL

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https://hg.mozilla.org/integration/gaia-central/rev/8944b09b141f
Author: Sam Joch <samuel@guiora.com>
Desc: Merge pull request #11912 from pivanov/bug-911962

Bug 911962 - [HD] Followup bug for Settings Icons r=samjoch

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https://hg.mozilla.org/integration/gaia-central/rev/a7ba705c556f
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 911962 - [HD] Followup bug for Settings Icons