docs: subject-case in docs does not match default

[mfairley]

The docs say "always" for 'subject-case' but on a fresh install I get

'subject-case': [
      2,
      'never',
      [ 'sentence-case', 'start-case', 'pascal-case', 'upper-case' ]
    ],

https://github.com/conventional-changelog/commitlint/blob/dddcc2834a24727ccb4cc63cdc4e7b7c06322e9b/docs/reference/rules.md?
plain=1#L273

[escapedcat]

Happy for a PR to fix the docs, thanks!