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

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https://hg.mozilla.org/integration/gaia-central/rev/20e7a2af5eaa
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #14983 from askeing/955963

Bug 955963 - Unxfail test_lockscreen_unlock_to_camera_with_passcode.py

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https://hg.mozilla.org/integration/gaia-central/rev/d75a7c6146e5
Author: askeing <askeing@gmail.com>
Desc: Bug 955963 - Unxfail test_lockscreen_unlock_to_camera_with_passcode.py