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

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https://hg.mozilla.org/integration/gaia-central/rev/b29ee48d5c0a
Author: Jan Keromnes <janx@linux.com>
Desc: Merge pull request #16472 from jankeromnes/devmenu

Bug 968454 - [Settings] New icon for Developer menu. r=arthurcc

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https://hg.mozilla.org/integration/gaia-central/rev/9a613b10dbe3
Author: Jan Keromnes <janx@linux.com>
Desc: Bug 968454 - [Settings] New icon for Developer menu. r=arthurcc
Bumping manifests a=b2g-bump