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

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https://hg.mozilla.org/integration/gaia-central/rev/864dfd0e6f53
Author: Arnau <arnau@arnaumarch.com>
Desc: Merge pull request #17451 from rnowm/986512

Bug 986512 - Switches [BB] remove transition

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https://hg.mozilla.org/integration/gaia-central/rev/7bc73c337dc8
Author: rnowm <arnau@arnaumarch.com>
Desc: Bug 986512 - Switches [BB] remove transition
Bumping manifests a=b2g-bump