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

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https://hg.mozilla.org/integration/gaia-central/rev/7125c8040844
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Merge pull request #12499 from comoyo/keyboard_slide_up

Bug 912028 - Background is visible on keyboard pop in. r=RudyL

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https://hg.mozilla.org/integration/gaia-central/rev/c5f1991f7a3e
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Bug 912028 - Background is visible on keyboard pop in