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

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https://hg.mozilla.org/integration/gaia-1_4/rev/f0275bec8d0a
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Merge pull request #23116 from davidflanagan/bug1056096

Bug 1056096: pick a preview size that is bigger than the screen

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https://hg.mozilla.org/integration/gaia-1_4/rev/b2709186a8f2
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 1056096: pick a preview size that is bigger than the screen

change the preview quality metric so that bigger numbers are better
Bumping manifests a=b2g-bump