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

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https://hg.mozilla.org/integration/gaia-central/rev/4252fd24e16f
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #15508 from EragonJ/bug-959497

Bug 959497 - [DSDS] SIM operator name needs to be updated

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https://hg.mozilla.org/integration/gaia-central/rev/345faadcc079
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 959497 - [DSDS] SIM operator name needs to be updated

- use AirplaneModeHelper
- add voicechange event listener
- update tests
Bumping manifests a=b2g-bump