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

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https://hg.mozilla.org/integration/gaia-central/rev/78d4df83015a
Author: RickyChien <RickyChien@users.noreply.github.com>
Desc: Merge pull request #25920 from RickyChien/bug-1070442

Bug 1070442 - Support building gaia apps in parallel r=@cctuan

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https://hg.mozilla.org/integration/gaia-central/rev/dc1e273bcf8d
Author: Ricky Chien <ricky060709@gmail.com>
Desc: Bug 1070442 - Support building gaia apps in parallel
Bumping manifests a=b2g-bump