fix: there is no need existing two i18n/zh*.toml files

[h1z3y3]

[languages.zh]
     contentDir = "content/zh"
     title = "TITLE"
     description = "DESC"
     languageName ="简体中文"
     weight = 1

If set the language zh, there are some errors, and there is no need existing two i18n/zh*.toml files.

The error on page:

close #732

[LisaFC]

This is great but are we sure it won't break anyone's site when they update - is anyone using the duplicate localization file?

[h1z3y3]

If we keep both of them, there would be an error: #732
So keeping them would occur errors too, for the latest hugo.