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

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https://hg.mozilla.org/integration/gaia-central/rev/7028b388b156
Author: Borja Salguero <borjasalguero@users.noreply.github.com>
Desc: Merge pull request #13695 from EragonJ/bug-937495

Bug 937495 - [Flatfish][FTU] update images and wordings

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https://hg.mozilla.org/integration/gaia-central/rev/9793d5089695
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 937495 - [Flatfish][FTU] update images and wordings

- update FTU images
- update wordings
- update CSS
- update images
- add l10nKeySuffix to handle localizations process
Bumping manifests a=b2g-bump