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

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https://hg.mozilla.org/integration/gaia-2_0/rev/2c906bc2a129
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #20955 from weigao123/push_master

Bug 1002327 - (master) add EventListener for mmi reply. r=Etienne.
(cherry picked from commit 8b742fde1be1226931eb198997994f4297375acd)
Bumping manifests a=b2g-bump