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

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https://hg.mozilla.org/integration/gaia-central/rev/1f9b2b1a7d7b
Author: RickyChien <RickyChien@users.noreply.github.com>
Desc: Merge pull request #25433 from RickyChien/bug-969215

Bug 969215 - Execute |make| should only build specific apps we modified r=@cctuan

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https://hg.mozilla.org/integration/gaia-central/rev/15a3a99171f0
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 969215 - Execute |make| should only build specific apps we modified
Bumping manifests a=b2g-bump