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

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https://hg.mozilla.org/integration/gaia-central/rev/584ef6ff3a7d
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Merge pull request #14811 from arcturus/bug-947859

Bug 947859 - Settings menu has stopped working in Contacts app for B2g desktop

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https://hg.mozilla.org/integration/gaia-central/rev/e8e832c9652f
Author: Francisco Jordano <arcturus@ardeenelinfierno.com>
Desc: Bug 947859 - Settings menu has stopped working in Contacts app for B2g desktop

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https://hg.mozilla.org/integration/gaia-central/rev/ed7f63072111
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #15084 from bobsilverberg/kb_lang

Bug 957144 - OSX b2g desktop failure | test_settings_change_keyboard_language.py

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https://hg.mozilla.org/integration/gaia-central/rev/c59a9d8e8cdc
Author: Bob Silverberg <bob.silverberg@gmail.com>
Desc: Bug 957144 - OSX b2g desktop failure | test_settings_change_keyboard_language.py