remove(layout): remove private layout

[neoFelhz]

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What kind of change does this PR introduce? (check one with "x")

• Bug fix
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• Code style update (formatting, local variables)
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Description

Remove the useless private layout.

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[kmahyyg]

@neoFelhz plz don't remove it.it's really useful if I want to share some private thing to my friend.

[neoFelhz]

@kmahyyg
If you had read the source code of the private layout, you will find how dirty the layout is: simply loading a tips instead of the post content.
I suggest you using hexo-blog-encrypt plugin. It's better than that.

[kmahyyg]

@neoFelhz ok ,that's nice.