Fixes the event for randomizing friction material

[pascal-roth]

Description

The current friction randomization event only selects a single random number in the given range and does not vary them. With the given PR, this is getting fixed, and there is a sampling of the entire given range.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Screenshots

Before	After

Checklist

• [x] I have run the pre-commit checks with ./isaaclab.sh --format
• [ ] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] I have updated the changelog and the corresponding version in the extension's config/extension.toml file
• [x] I have added my name to the CONTRIBUTORS.md or my name already exists there