docs: fix build badges link

[GridexX]

What is the purpose of this pull request? (put an "X" next to item)

[ ] Documentation update [ ] Bug fix [ ] New feature [x] Other, please explain:

What changes did you make? (Give an overview)

Fix the build badges URL of the README.md, as described on GitHub's issue: https://github.com/badges/shields/issues/8671

Which issue (if any) does this pull request address?

Is there anything you'd like reviewers to focus on?

[welcome[bot]]

🙌 Thanks for opening this pull request! You're awesome.