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

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https://hg.mozilla.org/integration/gaia-central/rev/c7a5af5dc4e9
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Merge pull request #16678 from jonallengriffin/modules

Bug 977366 - Allow make node_modules to use git mirror, r=gaye

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https://hg.mozilla.org/integration/gaia-central/rev/d61735aa8cc5
Author: Jonathan Griffin <jonallengriffin@gmail.com>
Desc: Bug 977366 - Allow make node_modules to use git mirror, r=gaye
Bumping manifests a=b2g-bump