Update babel-eslint to 9.0.0 - autoclosed

[renovate]

This PR contains the following updates:

Package	Type	Update	Change	References
babel-eslint	devDependencies	major	8.2.6 -> 9.0.0	source

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Release Notes

babel/babel-eslint

v9.0.0

Compare Source

v9.0.0

We've released v7: https://twitter.com/left_pad/status/1034204330352500736, so this just updates babel-eslint to use those versions internally. That in itself doesn't break anything but:

• Babel now supports the new decorators proposal by default, so we need to switch between the new and the old proposal. This is a breaking change.

To enable the legacy decorators proposal users should add a specific parser option:

{
  parserOptions: {
    ecmaFeatures: {
      legacyDecorators: true
    }
  }
}

• Babel removed the support for Node 4 , so I propagated that here.

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[coveralls]

Coverage remained the same at 100.0% when pulling 755daef on renovate/babel-eslint-9.x into b489419 on dev.