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

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https://hg.mozilla.org/integration/gaia-central/rev/f820619a50d4
Author: gitmai <mri@tid.es>
Desc: Merge pull request #20550 from gitmai/bug-1021383-fte-remove-white-drop-shadow

Bug 1021383 -[flame][cost control] Text in Usage Setup is not crisp
r=salva

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https://hg.mozilla.org/integration/gaia-central/rev/f6bb88c3d433
Author: mai <mri@tid.es>
Desc: Bug 1021383 -[flame][cost control] Text in Usage Setup is not crisp
Bumping manifests a=b2g-bump