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

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https://hg.mozilla.org/integration/gaia-central/rev/52a51b99d42c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #20968 from bebef1987/fix_cam

Bug 1030026 - Fix camera test_capture_a_video

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https://hg.mozilla.org/integration/gaia-central/rev/f47427b85d6b
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 1030026 - Fix camera test_capture_a_video
Bumping manifests a=b2g-bump