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

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https://hg.mozilla.org/integration/gaia-central/rev/64bfeb7bb602
Author: Sam Foster <sam@sam-i-am.com>
Desc: Merge pull request #19807 from sfoster/configurable-tutorial

Bug 1017314: Load tutorial config in a preload method. r=borjasalguero

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https://hg.mozilla.org/integration/gaia-central/rev/fc3b4d99af77
Author: Sam Foster <sfoster@mozilla.com>
Desc: Bug 1017314: Load tutorial config in a loadConfig method. r=borjasalguero

* Start tutorial preload in ftu UIManager.init
* Create per-layout tutorial config file, use l10nKey as title property name in config
* Refactor Tutorial to loadConfig/ensureConfig and update tests accordingly
* Remove unused data-maxstep attributes.
Bumping manifests a=b2g-bump