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

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https://hg.mozilla.org/integration/gaia-central/rev/c0860e7bf5c3
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Merge pull request #14202 from Rik/2nd-incomming-call-layout-923063-for-realz

Bug 923063 - Polish for incoming call in the call screen r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/9a791f0eab15
Author: Anthony Ricaud <anthony@ricaud.me>
Desc: Bug 923063 - Polish for incoming call in the call screen