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

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https://hg.mozilla.org/integration/gaia-central/rev/3e375bfada88
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #18821 from RickyChien/bug-998776

Bug 998776 - [Follow up of Bug 991446] Fix the broken coverage result on console r=@yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/8155814febd7
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 998776 - [Follow up of Bug 991446] Fix the broken coverage result on console
Bumping manifests a=b2g-bump