Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/2a9addc4e134
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #19699 from RickyChien/bug-936520-follow-up

Bug 936520 - Follow-up, update gaia_node_modules.revision r=me

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https://hg.mozilla.org/integration/gaia-central/rev/6795d7d12112
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 936520 - Follow-up, update gaia_node_modules.revision

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https://hg.mozilla.org/integration/gaia-central/rev/a598979586c4
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #19025 from RickyChien/bug-936520

Bug 936520 - [mocha] we can't see console.error in the console r=@julienw

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https://hg.mozilla.org/integration/gaia-central/rev/595e5893c1e1
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 936520 - [mocha] we can't see console.error in the console
Bumping manifests a=b2g-bump