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

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https://hg.mozilla.org/integration/gaia-central/rev/2f42e7e07abc
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #11646 from samjoch/bug-906630-HDBrowserReplaceBackTabArrowIcon

Bug 906630 - [HD][Browser] Replace back tab arrow icon

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https://hg.mozilla.org/integration/gaia-central/rev/0e0264090335
Author: Sam Joch <samuel@guiora.com>
Desc: Bug 906630 - [HD][Browser] Replace back tab arrow icon