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

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https://hg.mozilla.org/integration/gaia-central/rev/7f2c724873fa
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #16197 from RickyChien/issue-971507

Bug 971507 - Sync the changes in js-test-agent and gaia r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/6c9c06805dac
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 971507 - Sync the changes in js-test-agent and gaia
Bumping manifests a=b2g-bump