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

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https://hg.mozilla.org/integration/gaia-central/rev/4b3901a5adee
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Merge pull request #23656 from qdot/1061804-browser-opvar-followup

Bug 1061804 - Browser OpVar Customization Fixes

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https://hg.mozilla.org/integration/gaia-central/rev/d1ecfd6d9cc1
Author: Kyle Machulis <kyle@nonpolynomial.com>
Desc: Bug 1061804 - Browser OpVar Customization Fixes
Bumping manifests a=b2g-bump