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

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https://hg.mozilla.org/integration/gaia-central/rev/0503dc0b2c0e
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #14975 from yurenju/make-verification

Bug 954441 - Add more verification to integration test on build system f... r=@cctuan

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https://hg.mozilla.org/integration/gaia-central/rev/0209c4c2b321
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 954441 - Add more verification to integration test on build system