Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/37bdd8650158
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Merge pull request #15843 from comoyo/revert-964216

Revert Bug 964216

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https://hg.mozilla.org/integration/gaia-central/rev/d6674ef553ba
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Revert "Bug 964216 - Use build_stage to build keyboard app"

This reverts commit 7df9f588a3658d4579574aa574fec8e09744390e.

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https://hg.mozilla.org/integration/gaia-central/rev/c076dc7c0acc
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Revert "Bug 964216 - follow-up: fix getEnv issue"

This reverts commit 5d9e0fb1e8fb9ce521026aea0d9f9af45526ff05.
Bumping manifests a=b2g-bump