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

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https://hg.mozilla.org/integration/gaia-2_1/rev/6b18b0aa9390
Author: Eli Perelman <eli@eliperelman.com>
Desc: Bug 1067625 - Increasing timeout for performance tests to account for longer profile creation a=npotb r=lightsofapollo

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https://hg.mozilla.org/integration/gaia-2_1/rev/bce7630e5562
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1088352 - [Rocketbar] Resize frontWindow on system-resize r=alive
Bumping manifests a=b2g-bump