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

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https://hg.mozilla.org/integration/gaia-central/rev/b6786289c35c
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #25912 from jrburke/bug1093398-email-account-serial-action

Bug 1093398 - [Email] New account page appears again after tapping next r=asuth

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https://hg.mozilla.org/integration/gaia-central/rev/3bcf07744a87
Author: jrburke <jrburke@gmail.com>
Desc: Bug 1093398 - [Email] New account page appears again after tapping next
Bumping manifests a=b2g-bump