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

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https://hg.mozilla.org/integration/gaia-central/rev/7da66e2c4a0b
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #17821 from rnowm/990006

Bug 990006 - Change active state in dark themed [BB] buttons

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https://hg.mozilla.org/integration/gaia-central/rev/5bb9b3a60ff7
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 990006 - Change active state in dark themed [BB] buttons
Bumping manifests a=b2g-bump