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

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https://hg.mozilla.org/integration/gaia-central/rev/9073617f68b6
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #13168 from EragonJ/bug-926169

Bug 926169 - add backward compatibility check before landing gecko multi-sim API

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https://hg.mozilla.org/integration/gaia-central/rev/bf49409f161b
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 926169 - add backward compatibility check for mobileConnection

- use latest Gecko API and fallback when needed