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

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https://hg.mozilla.org/integration/gaia-central/rev/6b82ab58ac7e
Author: Rex KM Lee <rexboy@mozilla.com>
Desc: Merge pull request #11952 from rexboy7/fix-bug910185-4

bug 910185 - [Contact] Fix z-index problem when navigating panels.

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https://hg.mozilla.org/integration/gaia-central/rev/958b0f2edd94
Author: Rex Lee <rexboy@mozilla.com>
Desc: bug 910185 - [Contact] Fix z-index problem when navigating panels.