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

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https://hg.mozilla.org/integration/gaia-central/rev/307c9c3cda8f
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #23832 from yurenju/merge-build-apps-2

Bug 1053703 - Merge pre-app.js, app.js and post-app.js to one javascript...

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https://hg.mozilla.org/integration/gaia-central/rev/3be66e731951
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 1053703 - Merge pre-app.js, app.js and post-app.js to one javascript file r=gduan

Conflicts:
	Makefile
Bumping manifests a=b2g-bump