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

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https://hg.mozilla.org/integration/gaia-central/rev/98abf6bda1c1
Author: Jim Porter <squibblyflabbetydoo@gmail.com>
Desc: Merge pull request #15271 from jimporter/music-fix-seek-after-long-press

[Bug 951972] [music] cannot change progress bar after long tapping on "Random Play" icon; r=dkuo

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https://hg.mozilla.org/integration/gaia-central/rev/b34461e9fc8d
Author: Jim Porter <jporter@mozilla.com>
Desc: [Bug 951972] [music] cannot change progress bar after long tapping on "Random Play" icon
Bumping manifests a=b2g-bump