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

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https://hg.mozilla.org/integration/gaia-central/rev/12b7f192e1b1
Author: Sam Foster <sam@sam-i-am.com>
Desc: Merge pull request #21897 from sfoster/bug-1026159-2line-search-labels

Bug 1026159 - override search result label styles to wrap 2 lines, tighten up label spacing to spec. r=kgrandon

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https://hg.mozilla.org/integration/gaia-central/rev/431b9c60e787
Author: Sam Foster <sfoster@mozilla.com>
Desc: Bug 1026159 - override search result label styles to wrap 2 lines, tighten up grid and search results layout per spec. r=kgrandon
Bumping manifests a=b2g-bump