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

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https://hg.mozilla.org/integration/gaia-central/rev/b1ac3fa89a4d
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16484 from davehunt/bug974858

Bug 974858 - Make the lockscreen atom compatible with v1.3

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https://hg.mozilla.org/integration/gaia-central/rev/cf55471c08d2
Author: Dave Hunt <dave.hunt@gmail.com>
Desc: Bug 974858 - Make the lockscreen atom compatible with v1.3. r=zcampbell
Bumping manifests a=b2g-bump