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

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https://hg.mozilla.org/integration/gaia-central/rev/3bb26d78e259
Author: James Burke <jrburke@gmail.com>
Desc: Merge pull request #23225 from mozilla-b2g/revert-23219-bug1057277-signature-button

Revert "Bug 1057277 - [Email][Signature] Signature text displayed differ...

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https://hg.mozilla.org/integration/gaia-central/rev/c384f77fd4d3
Author: James Burke <jrburke@gmail.com>
Desc: Revert "Bug 1057277 - [Email][Signature] Signature text displayed different with UX specification"
Bumping manifests a=b2g-bump