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

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https://hg.mozilla.org/integration/gaia-central/rev/44556ba9c590
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #15249 from etiennesegonzac/bug-956220-landing

Bug 956220 - [Dialer]Adding a special call screen background for the emergency calls r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/b2705b49841e
Author: mukesh06.kumar <mukesh06.kumar@lge.com>
Desc: Bug 956220 - [Dialer]Adding a special call screen background for the emergency calls