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

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https://hg.mozilla.org/integration/gaia-central/rev/50936cff9847
Author: Hubert Figuière <hub@figuiere.net>
Desc: Merge pull request #22272 from eliperelman/bug-1045076-perf-timestamp-failsafe

Bug 1045076 - Add sanity check to timestamp handlers and return values r=hub

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https://hg.mozilla.org/integration/gaia-central/rev/8ff931be1624
Author: Eli Perelman <eli@eliperelman.com>
Desc: Bug 1045076 - Add sanity check to timestamp handlers and return values
Bumping manifests a=b2g-bump