📝 Docs: Update options output (help, errors)

[mark-wiemer]

Documentation Request Checklist

• I have read and agree to Mocha's Code of Conduct and Contributing Guidelines
• I have searched for related issues and issues with the faq label, but none matched my issue.
• I want to provide a PR to resolve this

Overview

• "pass-on-failing-test-suite": "Not fail test run if tests were failed", should be "Pass test run if only error is test failures"
• global: "List of allowed global variables", should be "List allowed global variables"
• --parallel runs test files in a non-deterministic order, and is mutually exclusive with should be "--parallel is mutually exclusive with"

Additional Info

I think we can bunch these three tiny fixups in one PR total :)

Semver-major?

[JoshuaKGoldberg]

Ehh, I don't think this needs to be a semver-major. It's just updating help/options output. Those aren't part of the public API.