[Bug Fix] Fix type name for tendon properties in from_files config

[KyleM73]

Tendon imports in from_files_cfg had a typo that prevented importing. This is resolved in this commit.

Type of change

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

Checklist

• [X] I have read and understood the contribution guidelines
• [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