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

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https://hg.mozilla.org/integration/gaia-central/rev/989c83a3ec25
Author: Aleh Zasypkin <aleh.zasypkin@gmail.com>
Desc: Merge pull request #21400 from azasypkin/bug-1034637-utils-tests

Bug 1034637 - [Messages] Utils.js unit tests are failing when run locally. r=julien

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https://hg.mozilla.org/integration/gaia-central/rev/7891166c14cc
Author: Aleh Zasypkin <azasypkin@mozilla.com>
Desc: Bug 1034637 - [Messages] Utils.js unit tests are failing when run locally. r=julien
Bumping manifests a=b2g-bump