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

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https://hg.mozilla.org/integration/gaia-central/rev/6c89720267bf
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #13573 from alivedise/bugzilla/936253/lock0orientation-on-lockscreen

Bug 936253 - Lock orientation on lockscreen, r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/67e8333f36d2
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 936253 - Lock orientation on lockscreen