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

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https://hg.mozilla.org/integration/gaia-central/rev/453391ee0372
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #19140 from mnjul/bug_972497_locked_callscreen_arrow

Bug 972497 - On locked call screen arrows are not the same

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https://hg.mozilla.org/integration/gaia-central/rev/c66d5731ede2
Author: John Lu [:mnjul] <jlu@mozilla.com>
Desc: Bug 972497 - On locked call screen arrows are not the same
Bumping manifests a=b2g-bump