openblas: add scikit-learn to passthru.tests

pkgs/development/libraries/science/math/openblas/default.nix

···
   '';
 
   passthru.tests = {
-    inherit (python3.pkgs) numpy scipy;
+    inherit (python3.pkgs) numpy scipy scikit-learn;
     inherit ceres-solver giac octave opencv;
   };