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

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https://hg.mozilla.org/integration/gaia-central/rev/1423886fd6f4
Author: ochameau <poirot.alex@gmail.com>
Desc: Merge pull request #19057 from ochameau/discardSources

Bug 1001348 - Disable discardSystemSource js optim when DEVICE_DEBUG=1. r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/67b7cdc68814
Author: Alexandre Poirot <poirot.alex@gmail.com>
Desc: Bug 1001348 - Disable discardSystemSource js optim when DEVICE_DEBUG=1.
r=timdream
Bumping manifests a=b2g-bump