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

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https://hg.mozilla.org/integration/gaia-central/rev/3169d5550e74
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #15707 from EragonJ/bug-958412

Bug 958412 - [Gaia][DSDS] move simcard detection logic to system app

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https://hg.mozilla.org/integration/gaia-central/rev/e228f95c86e5
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 958412 - [Gaia][DSDS] move simcard detection logic to system app

- add sim_settings_helper
- add related test
- update slot.isAbsent()
Bumping manifests a=b2g-bump