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

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https://hg.mozilla.org/integration/gaia-central/rev/db17f22d019a
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #18602 from jimporter/music-update-hidden-scrubber

Bug 1000214 - [music] Update progress bar when display is suspended and ...

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https://hg.mozilla.org/integration/gaia-central/rev/a6b9c324e768
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1000214 - [music] Update progress bar when display is suspended and audio paused; r=dkuo
Bumping manifests a=b2g-bump