Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/2927b8897b18
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #16434 from timdream/httpd-build-stage

Bug 974246 - Find file in build_stage if it doesn't exist in app directory +shepherd

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https://hg.mozilla.org/integration/gaia-central/rev/2626c9ee594b
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Bug 974246 - Find file in build_stage if it doesn't exist in app directory

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https://hg.mozilla.org/integration/gaia-central/rev/f9701428abb8
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #16394 from allstarschh/Bug972788

Bug 972788 : launch Browser after reading a NFC tag.

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https://hg.mozilla.org/integration/gaia-central/rev/57315783242c
Author: allstars.chh <allstars.chh@gmail.com>
Desc: Bug 972788 : launch Browser after reading a NFC tag.
Bumping manifests a=b2g-bump