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

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https://hg.mozilla.org/integration/gaia-central/rev/ff5c4db0d9c8
Author: Timothy Guan-tin Chien <timdream@gmail.com>
Desc: Merge pull request #15365 from larryxiao/master

Bug 959447 - Remove twittershare test app, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/c7be1fce544d
Author: Xiao Di <xiaodi@sjtu.edu.cn>
Desc: Bug 959447 - Remove twittershare test app

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https://hg.mozilla.org/integration/gaia-central/rev/2c5c6f8a5b40
Author: EragonJ <eragonj@eragonj.me>
Desc: Merge pull request #15284 from EragonJ/bug-956424

Bug 956424 - SIM Security enabled/disabled information is wrong

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https://hg.mozilla.org/integration/gaia-central/rev/065166b89bf0
Author: EragonJ <eragonj@eragonj.me>
Desc: Bug 956424 - SIM Security enabled/disabled information is wrong

- add related tests
- fix enabled/disabled information