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

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https://hg.mozilla.org/integration/gaia-central/rev/f91f21507a8c
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #20219 from gasolin/issue-1022480

Bug 1022480 - permission-request screen has a bonus message about 'Selec..., r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/60e929b212f0
Author: gasolin <gasolin@gmail.com>
Desc: Bug 1022480 - permission-request screen has a bonus message about 'Select a camera'
Bumping manifests a=b2g-bump