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

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https://hg.mozilla.org/integration/gaia-2_0/rev/f4d654fb6acb
Author: Julien Wajsberg <felash@gmail.com>
Desc: Merge pull request #24298 from julienw/1018896-v2.0-firefox-version

Bug 1018896 - In Travis, fetch the right version of Firefox and b2g r=me...

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https://hg.mozilla.org/integration/gaia-2_0/rev/2ff1bd0e430b
Author: Julien Wajsberg <felash@gmail.com>
Desc: Bug 1018896 - In Travis, fetch the right version of Firefox and b2g r=me a=tests
Bumping manifests a=b2g-bump