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

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https://hg.mozilla.org/integration/gaia-central/rev/2c493cf2c702
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 928968 - Add a command to the gaia command line tool to print the applications installed. r=zcampbell r=rwood