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

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https://hg.mozilla.org/integration/gaia-1_3/rev/4946436550b1
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #19956 from davidflanagan/bug996455

Bug 996455: use device pixels, not css pixels when determining if an EXIF preview is big enough r=pdahiya a=1.3+,hkoka

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https://hg.mozilla.org/integration/gaia-1_3/rev/ef90f0a82db9
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 996455: use device pixels, not css pixels when determining if an EXIF preview is big enough
Bumping manifests a=b2g-bump