Fix typos in function list

[ggorlen]

Context

This PR has a few simple typo fixes to the docs, changelog update seems unnecessary.

How did you test your changes?

No testing necessary.

Types of changes

• [ ] Breaking change (a fix or a feature because of which an existing functionality doesn't work as expected anymore)
• [ ] New feature or improvement (a non-breaking change that adds functionality)
• [ ] Bug fix (a non-breaking change that fixes an issue)
• [ ] Additional language file, or a change to an existing language file (translations)
• [x] Change to the documentation

Related issues:

1. Fixes #...

Checklist:

• [x] I have reviewed the guidelines about Contributing to HyperFormula and I confirm that my code follows the code style of this project.
• [x] I have signed the Contributor License Agreement.
• [x] My change is compliant with the OpenDocument standard.
• [x] My change is compatible with Microsoft Excel.
• [x] My change is compatible with Google Sheets.
• [ ] I described my changes in the CHANGELOG.md file.
• [x] My changes require a documentation update.
• [ ] My changes require a migration guide.

[AMBudnik]

Hi @ggorlen

Thank you for taking the time to share the pull request and for signing our CLA.

I will ask my colleague to review it.

[sequba]

@ggorlen thank you for the contribution. I'm merging this pull request.

[AMBudnik]

Hi @ggorlen

Thank you again for sharing this pull request.

Proposed fixes are merged and released under HyperFormula v3.0.1.