Remove FortUTF CMake 3.20 requirement in README

What is the bug

The CMake version requirement for FortUTF is downgraded to 3.17. Therefore, the line in README is no longer required.

How do you fix it

A typo is also fixed.

How urgent is the bugfix

• I need it as soon as possible
• I can wait for a couple of days
• None of my current codes is directly affected

Mandatory steps before review

• Gitlab CI passes (Hint: use make format for linting)
• Bugfix is covered by additional unit tests
• Mark the merge request as ready by removing Draft:

Mandatory steps before merge

• Reviewed by a maintainer
• Incorporate review suggestions
• Remember to edit the commit message and select the proper changelog category (feature/bugfix/other)

You are not supposed to merge this request by yourself, the maintainers of fortan-support take care of this action!