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

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https://hg.mozilla.org/integration/gaia-central/rev/138a50b76561
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #17642 from crdlc/bug-988172

Bug 988172 - Create datastore for bookmarks and extract the UI to add th...

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https://hg.mozilla.org/integration/gaia-central/rev/8985d0c3b07a
Author: crdlc <crdlc@tid.es>
Desc: Bug 988172 - Create datastore for bookmarks and extract the UI to add them to system
Bumping manifests a=b2g-bump