No need to specify `REVIEWDOG_GITHUB_API_TOKEN` manually

[paddyroddy]

REVIEWDOG_GITHUB_API_TOKEN is specified as required in the docs https://redhat-documentation.github.io/vale-at-red-hat/docs/main/user-guide/using-vale-github-action. It is not required as vale does this itself, e.g. https://github.com/errata-ai/vale-action/blob/dcded780f1ff68e2558e802a165a484a4a3e2fb8/src/main.ts#L52