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

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https://hg.mozilla.org/integration/gaia-2_0/rev/8536587e8be9
Author: Ryan VanderMeulen <rvandermeulen@mozilla.com>
Desc: Merge pull request #21354 from justindarc/bug1031012-v2.0

Bug 1031012 - [B2G][Camera]Self-timer cannot be canceled

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https://hg.mozilla.org/integration/gaia-2_0/rev/5cd63a65a51e
Author: Justin D'Arcangelo <justindarc@gmail.com>
Desc: Bug 1031012 - [B2G][Camera]Self-timer cannot be canceled
Bumping manifests a=b2g-bump