libsvm: 3.20 -> 3.22

Semi-automatic update. These checks were done:

- built on NixOS
- ran `/nix/store/97a1nnpdah29fs3v274lnzk0hcyhncg3-libsvm-3.22/bin/svm-scale help` got 0 exit code
- ran `/nix/store/97a1nnpdah29fs3v274lnzk0hcyhncg3-libsvm-3.22/bin/svm-train help` got 0 exit code
- found 3.22 in filename of file in /nix/store/97a1nnpdah29fs3v274lnzk0hcyhncg3-libsvm-3.22