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

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https://hg.mozilla.org/integration/gaia-central/rev/8ca71fb4f413
Author: GaryChen,PYChen <mmm198219@gmail.com>
Desc: Merge pull request #17701 from mpizza/Bug_979787_APPLIST_for_multiple_devices

Bug 979787 - [GAIA][BUILD SYSTEM] new apps.list structure for multiple-devices. r=yuren.

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https://hg.mozilla.org/integration/gaia-central/rev/b4ce9210f9cb
Author: mpizza <mmm198219@gmail.com>
Desc: Bug 979787 - [GAIA][BUILD SYSTEM] new apps.list structure for multiple-devices. r=yuren.
Bumping manifests a=b2g-bump