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

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https://hg.mozilla.org/integration/gaia-central/rev/1864f4620b32
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #25255 from alivedise/bugzilla/1062819_pickup_rebased/mobile-connection-core

Bugzilla/1062819 pickup rebased/mobile connection core, r=etienne+arthurcc+jaoo

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https://hg.mozilla.org/integration/gaia-central/rev/f840cb988ede
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 1062819 - Implement MobileConnectionCore and corresponding sub system
Bumping manifests a=b2g-bump