Remove duplicate variant + value pairs from completions

[thecrypticace]

This happens if you register variant like peer-hover because Tailwind itself defines a peer variant that has several values — one of which is hover.

Basically, this config no longer produces multiple completions for peer-hover:

export default {
  plugins: [
    ({ addVariant }) => {
      addVariant("peer-hover", "[data-hoverable] .peer:hover ~ &");
    }
  ]
}

Fixes tailwindlabs/tailwindcss#12187