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

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https://hg.mozilla.org/integration/gaia-central/rev/90c92ca23e54
Author: Jim Porter <jporter@mozilla.com>
Desc: Merge pull request #23125 from jimporter/ringtones-new-sounds

Bug 1046399 - (2.1-visual-refresh)[Ringtones] - Add New Tones

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https://hg.mozilla.org/integration/gaia-central/rev/18bc013b9eac
Author: Jim Porter <jporter@mozilla.com>
Desc: Bug 1046399 - (2.1-visual-refresh)[Ringtones] - Add New Tones
Bumping manifests a=b2g-bump