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

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https://hg.mozilla.org/integration/gaia-central/rev/3dc289644918
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #21258 from alivedise/bugzilla/1032068_master/drop-activity-on-demand

Bug 1032068 - Maintain id pool of activity chaining instances to keep on...r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/a2b8d2aa8831
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1032068 - Maintain id pool of activity chaining instances to keep only one chaining
Bumping manifests a=b2g-bump