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

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https://hg.mozilla.org/integration/gaia-central/rev/6a400c1c3e73
Author: albertopq <albert.pastor@gmail.com>
Desc: Merge pull request #25228 from albertopq/1082911-shb-smart-collections

Bug 1082911 - Adding integration tests for SHB homescreen r=mhenretty

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https://hg.mozilla.org/integration/gaia-central/rev/a8aea966c46a
Author: albertopq <apastor@mozilla.com>
Desc: Bug 1082911 - Adding integration tests for SHB homescreen
Bumping manifests a=b2g-bump