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

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https://hg.mozilla.org/integration/gaia-central/rev/4fc7e8aeff02
Author: Rex KM Lee <rexboy@mozilla.com>
Desc: Merge pull request #11828 from rexboy7/fix-bug907443

Bug 907443 - declare callsHandler.activeCall correctly (regression of bug 902983)

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https://hg.mozilla.org/integration/gaia-central/rev/6a2cb8a39fa4
Author: Rex Lee <rexboy@mozilla.com>
Desc: Bug 907443 - [dialer] declare callsHandler.activeCall correctly (regression of bug 902983)