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

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https://hg.mozilla.org/integration/gaia-1_4/rev/878aa8994b76
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #18306 from davidflanagan/bug995432-v1.4

Merge pull request #18249 from davidflanagan/bug995432

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https://hg.mozilla.org/integration/gaia-1_4/rev/c84a75f8f5bb
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #18249 from davidflanagan/bug995432

Bug 995432: simple continuous auto focus support r=jdarcangelo(cherry picked from commit 289f131cc65dbf35f69924254a71e76628d2e36d)
Bumping manifests a=b2g-bump