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

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https://hg.mozilla.org/integration/gaia-central/rev/cd7bf7d6b4d1
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #24586 from davidflanagan/bug1074262-master

Merge pull request #24585 from davidflanagan/bug1074262 r=dmarcos

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https://hg.mozilla.org/integration/gaia-central/rev/6c6f24758f70
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #24585 from davidflanagan/bug1074262

Bug 1074262: workaround graphics bug with will-change:opacity r=dmarcos(cherry picked from commit dc6d78742a0b327dce7be99245244f66db6f8279)
Bumping manifests a=b2g-bump