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

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https://hg.mozilla.org/integration/gaia-central/rev/c7680ec70deb
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #24358 from davidflanagan/bug1070207

Bug 1070207: create a suite of Gallery test images r=justindarc

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https://hg.mozilla.org/integration/gaia-central/rev/b8408813633c
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 1070207: create a suite of Gallery test images
Bumping manifests a=b2g-bump