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

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https://hg.mozilla.org/integration/gaia-central/rev/4ff1edbd6eac
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #16694 from RickyChien/bug-977435

Bug 977435 - Better UI for TestAgent app: move execute button to top panel r=@yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/d3258422b206
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 977435 - Better UI for TestAgent app: more powerful top panel
Bumping manifests a=b2g-bump