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

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https://hg.mozilla.org/integration/gaia-central/rev/57b0fc0c1199
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #12213 from EragonJ/bug-911681

Bug 911681 - [FTU] replace tutorial images for large device

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https://hg.mozilla.org/integration/gaia-central/rev/b30446d3a85b
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 911681 - [FTU] replace tutorial images for large device

- use IAC
- add IAC handler for system app
- add IAC handler tests
- add tablet support
- add TutorialSteps for two devices
- add Tutorial related tests
- update media_playback to use IAC handler