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

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https://hg.mozilla.org/integration/gaia-central/rev/42e71c9378f5
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #20274 from EragonJ/bug-968619

Bug 968619 - [Settings] add marionette test for airplane mode

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https://hg.mozilla.org/integration/gaia-central/rev/d5308b4bd238
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 968619 - [Settings] add marionette test for airplane mode
Bumping manifests a=b2g-bump