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

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https://hg.mozilla.org/integration/gaia-central/rev/a328570f9bec
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #18863 from benfrancis/999141

Bug 999141 - Fix statusbar visibility on lockscreen r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/7bc9c1b9133e
Author: Ben Francis <ben@tola.me.uk>
Desc: Bug 999141 - Fix statusbar visibility on lockscreen
Bumping manifests a=b2g-bump