Bumping gaia.json for 2 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/f6d991032216
Author: Ben Kelly <bkelly@mozilla.com>
Desc: Merge pull request #13966 from wanderview/contacts-onscreen-style

Bug 942398: Do not remove missing styles while scrolling.  r=arcturus

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https://hg.mozilla.org/integration/gaia-1_2/rev/57261b006d6d
Author: Ben Kelly <bkelly@mozilla.com>
Desc: Merge pull request #13964 from wanderview/contacts-imgloader-timeout

Bug 942397: Throttle setTimeout calls in imgLoader.  r=crdlc