Bumping gaia.json for 1 gaia-1_2 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_2/rev/08a41d8119c0
Author: Lyall Jonathan Di Trapani <lj.ditrapani@gmail.com>
Desc: Bug 935319 - Improve gaia-ui-tests documentation for users getting starting with b2g-desktop builds. r=dhunt