Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f6e33b4f0225
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #15316 from cctuan/955992

Bug 955992 - Running install-gaia.js on node.js

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https://hg.mozilla.org/integration/gaia-central/rev/65151017b4e5
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 955992 - Running install-gaia.js on node.js

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https://hg.mozilla.org/integration/gaia-central/rev/1ef8f5fd26cb
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #15717 from bebef1987/camera

Bug 958524 - Fix test_camera_flash_mode to use a manifest tag

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https://hg.mozilla.org/integration/gaia-central/rev/f0e8a8e6fdb8
Author: Bebe <bebe@mozilla.ro>
Desc: Bug 958524 - Fix test_camera_flash_mode to use a manifest tag
Bumping manifests a=b2g-bump