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

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https://hg.mozilla.org/integration/gaia-central/rev/c5dbcf712337
Author: Carmen Jiménez <cjc@tid.es>
Desc: Merge pull request #18290 from mcjimenez/bug996048

Bug 996048 - variant.js is not needed not used anymore on the communications app

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https://hg.mozilla.org/integration/gaia-central/rev/5e31cc631b86
Author: Carmen Jimenez Cabezas <cjc@tid.es>
Desc: Bug 996048 - variant.js is not needed not used anymore on the communications app
Bumping manifests a=b2g-bump