These packages are now in the guix-science-nonfree package (commit
79067f0beaf45c67c92402922ae98f4130d07300).

* non-free/mkl.scm (mkl, mkl-2019, %intel-mkl-url)
(make-intel-oneapi-mkl, intel-oneapi-mkl+main, intel-oneapi-mkl+devel)
(intel-oneapi-mkl+common+devel, intel-oneapi-mkl+meta): Remove.
(mkl): Redefine as a deprecated alias for ‘intel-oneapi-mkl’.