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

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https://hg.mozilla.org/integration/gaia-central/rev/debdbd06e397
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #15033 from EragonJ/bug-956642

Bug 956642 - [Settings] add marionette for language change

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https://hg.mozilla.org/integration/gaia-central/rev/a12ea9eeb693
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 956642 - [Settings] add marionette for language change

- add marionette test for language
Bumping manifests a=b2g-bump