Remove symlinks of versioned to unversioned engine libraries

[iche033]

🦟 Bug fix

Summary

There are no longer versioned libraries so we can removed these symlinks. Same thing was done in gazebosim/gz-physics#747

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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