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

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https://hg.mozilla.org/integration/gaia-central/rev/b788acc2ea61
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #19575 from RickyChien/bug-1006357

Bug 1006357 - make test agent to run tests from all apps locally and in travis r=@yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/1835bac8f126
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 1006357 - make test agent to run tests from all apps locally and in travis
Bumping manifests a=b2g-bump