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

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https://hg.mozilla.org/integration/gaia-central/rev/1a88d90f1021
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #24375 from alivedise/bugzilla/1065720_master/attention-window-under-homescreen-window

Bug 1065720 - Upgrade the zindex of attention window before opened. r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/96905c64a978
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1065720 - Upgrade the zindex of attention window before opened.
Bumping manifests a=b2g-bump