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

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https://hg.mozilla.org/integration/gaia-central/rev/be6a331fe0b7
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #20403 from yzen/bug-997240

Bug 997240 - added proper screen reader semantics to the homescreen's pa...

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https://hg.mozilla.org/integration/gaia-central/rev/233ac142fe24
Author: Yura Zenevich <yzenevich@mozilla.com>
Desc: Bug 997240 - added proper screen reader semantics to the homescreen's pagination bar.
Bumping manifests a=b2g-bump