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

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https://hg.mozilla.org/integration/gaia-central/rev/e6999e12dfcc
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #20037 from yglazko/fmd_erase_fix

Bug 1020580 Proposed Fix for FMD Erase Not Working

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https://hg.mozilla.org/integration/gaia-central/rev/59d8d7683615
Author: yglazko <yglazko@yglazko.local>
Desc: Bug 1020580 - Handle getDeviceStorage returning null in Find My Device.
Bumping manifests a=b2g-bump