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

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https://hg.mozilla.org/integration/gaia-central/rev/451250fa7e7c
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #17952 from rnowm/989933

Bug 989933 - Create green themed header [BB] for comms apps r=pivanov

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https://hg.mozilla.org/integration/gaia-central/rev/08ef8aad0ec8
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 989933 - Create green themed header [BB] for comms apps
Bumping manifests a=b2g-bump