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

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https://hg.mozilla.org/integration/gaia-central/rev/2a7bacbad0ab
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #15641 from svic/Bug_959104

Bug 959104: Check screen and lock state at the same time.

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https://hg.mozilla.org/integration/gaia-central/rev/dd84bdb16c06
Author: Garner Lee <garner.lee@telekom.com>
Desc: Bug 959104: Check screen and lock state at the same time.
Bumping manifests a=b2g-bump