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

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https://hg.mozilla.org/integration/gaia-central/rev/f15f6d17ed80
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #13019 from etiennesegonzac/bug-852314-dialer-keypad-enabling

Bug 852314 - Enabling the oncall keypad asap according to the 3GPP spec. r=ferjm

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https://hg.mozilla.org/integration/gaia-central/rev/b63ab0aa841f
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 852314 - Enabling the oncall keypad asap according to the 3GPP spec.