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

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https://hg.mozilla.org/integration/gaia-central/rev/c8c6a86eeecf
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #16794 from crdlc/bug-978739

Bug 978739 - After rebooting users are not able to delete/open bookmarks from...

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https://hg.mozilla.org/integration/gaia-central/rev/129f294dcb2b
Author: crdlc <crdlc@tid.es>
Desc: Bug 978739 - After rebooting users are not able to delete bookmarks from homescreen
Bumping manifests a=b2g-bump