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

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https://hg.mozilla.org/integration/gaia-central/rev/15127e0e47b5
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #12321 from rnowm/action_menu_header

Bug 916087 - [BB] [Action Menu] Add functionality to headers

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https://hg.mozilla.org/integration/gaia-central/rev/1960cd7937a8
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 916087 - [BB] [Action Menu] Add functionality to headers