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

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https://hg.mozilla.org/integration/gaia-central/rev/766782d40fc2
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #16516 from zacc/bug_975374

Bug 975374 - Tag python tests with tag for manual smoketests

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https://hg.mozilla.org/integration/gaia-central/rev/3737d04237d6
Author: Zac Campbell <zcampbell@mozilla.com>
Desc: Bug 975374 - Tag python tests with tag for manual smoketests
Bumping manifests a=b2g-bump