Drop "experimental" from README.md

[jakirkham]

Fixes #188

Description

This is no longer experimental. So drop this caveat from the README.

Checklist - did you ...

• Add a file to the news directory (using the template) for the next release's release notes?
• Add / update necessary tests?
• Add / update outdated documentation?

[jakirkham]

Dropped "experimental", but left "new". Idk if we want to drop both. Please let me know what you think :)

[jezdez]

Nah, this is fine, thank you!

[jakirkham]

Looks like the other CI runs need approval

Also not sure what this pre-commit.ci error means:

Insert license in comments...............................................Failed
- hook id: insert-license
- exit code: 1
- files were modified by this hook

[jaimergp]

Looks like the other CI runs need approval

Also not sure what this pre-commit.ci error means:

Insert license in comments...............................................Failed
- hook id: insert-license
- exit code: 1
- files were modified by this hook

This is being handled in #187, no worries.

[jakirkham]

Thank you both! 🙏