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

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https://hg.mozilla.org/integration/gaia-central/rev/757f8293fa9a
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Merge pull request #13349 from jonallengriffin/testapp

Bug 926280 - Add SMS perms to test container app, r=ahal, a=test-only

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https://hg.mozilla.org/integration/gaia-central/rev/d3bd97b2ba02
Author: Jonathan Griffin <jonallengriffin@gmail.com>
Desc: Bug 926280 - Add SMS perms to test container app, r=ahal, a=test-only