Fix toString instance for edge styles

What does this MR do?

Previously the toString instance would print e.g. styledashed, while it should be dashed.

I used the web IDE for this, apparently it also converted the file to Unix line endings...

Related issues

Changes to public APIs

Author's checklist (required)

See CONTRIBUTING.md for the rationale behind these items:

• The commit history does not contain merges (use git rebase -i master if it does)
• Intermediate commits compile (use git rebase -i master if not)
• Newly added code follows the Platform code style
• Newly added code is documented
• If bugs have been solved, tests have been added
• Appropriate types have been used, especially in APIs
• If efficiency is part of the acceptance criteria of the issue, a benchmark is provided
• A changelog entry has been added if required. See CONTRIBUTING.md