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

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https://hg.mozilla.org/integration/gaia-central/rev/156e4c02bba8
Author: Carsten Book -Tomcat- <cbook@mozilla.com>
Desc: Revert "Bug 943845 - [Gallery] There is a little delay between before rendering the images while panning. r=djf" for mochitest bustage

This reverts commit a1930cf9a47f1461e28305316517c114e1a681c2.

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https://hg.mozilla.org/integration/gaia-central/rev/be63dcb7ecc9
Author: Julien Wajsberg <felash@gmail.com>
Desc: Revert "Merge pull request #16866 from lightsofapollo/fix-bad-things"
Revert Bug 979435 because the network issue looks resolved.

This reverts commit 4b0e62c713d83a36d4db42556625a2bc2b44e3f2, reversing
changes made to 6781459a49642ca0eb7ec3e95667808d5d77b656.
Bumping manifests a=b2g-bump