Fix ledc example

[Aemulation]

Submission Checklist 📝

• I have updated existing examples or added new ones (if applicable).
• I have used cargo fmt command to ensure that all changed code is formatted correctly.
• I have used cargo clippy command to ensure that all changed code passes latest Clippy nightly lints.
• My changes were added to the CHANGELOG.md in the proper section.

Pull Request Details 📖

Description

LedcTimerDriver returns a Result while get_max_duty doesn't.

Testing

Describe how you tested your changes.

[ivmarkov]

Thanks!