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

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https://hg.mozilla.org/integration/gaia-central/rev/56f683bbe94a
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #21310 from eeejay/bug-1033825

Bug 1033825 - Remove role="button" style selectors. r=Sergi

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https://hg.mozilla.org/integration/gaia-central/rev/2af8fbb7d262
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 1033825 - Remove role="button" style selectors.
Bumping manifests a=b2g-bump