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

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https://hg.mozilla.org/integration/gaia-2_0/rev/2b9977bb309d
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #23639 from alivedise/bugzilla/1055299_v2.0/v4

Bug 1055299: Make visibility manager know search window, r=kgrandon

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https://hg.mozilla.org/integration/gaia-2_0/rev/29100682d8f6
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1055299: Ignore continuous app launch request in homescreen side and send homescreen to background while rocketbar is open in system side
Bumping manifests a=b2g-bump