Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-2_0/rev/c8f6b3b28f76
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Revert "Bug 1031524 - Search Engine based on MNC/MCC in browser.json is not included in the Settings -> Homescreen -> Search Engine. r=benfrancis"

This reverts commit de7448291f57121314dcfbad0a4fa966b2308bd4.
Bumping manifests a=b2g-bump