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

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https://hg.mozilla.org/integration/gaia-central/rev/57b50f9c68ce
Author: AndreiH <andrei.hutusoru@gmail.com>
Desc: Merge pull request #14926 from askeing/952899

Bug 952899 - Fix test_receive_active_sync_email.py

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https://hg.mozilla.org/integration/gaia-central/rev/0bf4ff4c8864
Author: askeing <askeing@gmail.com>
Desc: Bug 952899 - Fix test_receive_active_sync_email.py