Fix error on intel macOS

[yutannihilation]

checking dependencies in R code ... NOTE
Error: unable to load shared object '/Volumes/Builds/packages/big-sur-x86_64/results/4.5/string2path.Rcheck/string2path/libs/string2path.so':
  dlopen(/Volumes/Builds/packages/big-sur-x86_64/results/4.5/string2path.Rcheck/string2path/libs/string2path.so, 0x0006): symbol not found in flat namespace '_kCTFontURLAttribute'
Call sequence:
3: dyn.load(file, DLLpath = DLLpath, ...)
2: library.dynam(lib, package, package.lib)
1: loadNamespace(package, lib.loc)
Execution halted

[yutannihilation]

It seems this error is not reproducible on CI, so I'm not sure if this actually fixes the error on CRAN...

https://github.com/yutannihilation/string2path/actions/runs/24401594366/job/71273382059