docs: fix broken link and outdated comment

[seeM]

Description (e.g. "Related to ...", etc.)

Fixes a broken link to lsprotocol in the docs, as well as an outdated comment (I think) pointing to pygls.lsp.methods which should point to lsprotocol too. Also a typo.

It's such a small change that I don't think contributors or changelog need to be updated.

Code review checklist (for code reviewer to complete)

• [x] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• [x] Title summarizes what is changing
• [x] Commit messages are meaningful (see this for details)
• [x] Tests have been included and/or updated, as appropriate
• [x] Docstrings have been included and/or updated, as appropriate
• [x] Standalone docs have been updated accordingly
• [x] CONTRIBUTORS.md was updated, as appropriate
• [x] Changelog has been updated, as needed (see CHANGELOG.md)

[tombh]

This is great! Thank you ♥️

[seeM]

My pleasure! And thank you for your work on pygls! 😄