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

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https://hg.mozilla.org/integration/gaia-central/rev/a9da04dbeb90
Author: RickyChien <ricky060709@gmail.com>
Desc: Merge pull request #18409 from RickyChien/bug-991446

Bug 991446 - Fix coverage when tests are run in their own sandbox r=@yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/fe44d456e0bc
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 991446 - Fix coverage when tests are run in their own sandbox
Bumping manifests a=b2g-bump