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

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https://hg.mozilla.org/integration/gaia-central/rev/351c20bccde1
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Merge pull request #25240 from mikehenrty/bug-1084137-waive-xrays

Bug 1084137 - Clone threads intro right compartment for the mobile messa...

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https://hg.mozilla.org/integration/gaia-central/rev/e15eb8e4f505
Author: Michael Henretty <michael.henretty@gmail.com>
Desc: Bug 1084137 - Clone threads intro right compartment for the mobile message mock
Bumping manifests a=b2g-bump