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

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https://hg.mozilla.org/integration/gaia-1_4/rev/210747516e1b
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #20365 from julienw/1000337-v1.4-fix-notifications-test

Bug 1000337 - Correct notification title checking in integration test…

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https://hg.mozilla.org/integration/gaia-1_4/rev/21095e54ddd6
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Bug 1000337 - Correct notification title checking in integration test a=tests-only
Bumping manifests a=b2g-bump