Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/2125d454811e
Author: Shih-Chiang Chien <schien@mozilla.com>
Desc: Bug 984274 - add required permission for mochitest. r=fabrice
Bumping manifests a=b2g-bump