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

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https://hg.mozilla.org/integration/gaia-central/rev/73d7af68e084
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #21524 from empoalp/bug_1030417

Bug 1030417 - aria role key for number keyboard keys

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https://hg.mozilla.org/integration/gaia-central/rev/79258ab705e7
Author: David Garcia <davidg@tid.es>
Desc: Bug 1030417 - aria role key for number keyboard keys
Bumping manifests a=b2g-bump