doc(README.md): remove broken link

Author: rouson

README.md

@@ -68,4 +68,3 @@ meson install -C build
 - [netlib/dfftpack1.0(fftpack4.0)](http://www.netlib.org/fftpack/)
 - [Documents of fft routines in GNU/gsl based on `netlib/fftpack`](https://www.gnu.org/software/gsl/doc/html/fft.html#)
 - [Documents of scipy.fftpack](https://docs.scipy.org/doc/scipy/reference/fftpack.html)
-- [NACR/FFTPACK 5.1](https://www2.cisl.ucar.edu/resources/legacy/fft5)