Remove extraneous format specifier associated with random ctest segfaults

[dfnca]

Summary

There was an unused %s format specifier in C binding test example 2 that apparently could cause memory corruption.
This addresses Issue #20

Changes

Removed extraneous format specifier (see diff)

Testing

1. made change on a pristine branch
2. rebuilt release version, same compiler and settings (gcc 13.3.0)
3. Invoked ctest repeatedly, always 100% pass where previously example 2 would sometimes cause a segmentation fault

Compatibility / Numerical behavior

• [ X] No expected changes to numerical results
• Expected changes (explain and provide validation)

[markleader]

Thanks @dfnca , merging