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

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https://hg.mozilla.org/integration/gaia-central/rev/5b101244e72e
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #16773 from yurenju/bug977630

Bug 977630 - [Single Variant] Builds Generation with Single Variant is not working r=@acperez

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https://hg.mozilla.org/integration/gaia-central/rev/fb6c85102af0
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 977630 - [Single Variant] Builds Generation with Single Variant is not working
Bumping manifests a=b2g-bump