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

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https://hg.mozilla.org/integration/gaia-central/rev/6e971c6a9f94
Author: Greg Weng <snowmantw@gmail.com>
Desc: Merge pull request #15100 from snowmantw/issue935148

Bug 935148 - Double touch on the slide would make Lockscreen can't unlock

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https://hg.mozilla.org/integration/gaia-central/rev/5391546bcfc0
Author: Greg Weng <snowmantw@gmail.com>
Desc: Bug 935148 - Double touch on the slide would make Lockscreen can't unlock