Pin scikit-learn to !=0.23.0

Author: PrimozGodec

requirements-core.txt

@@ -1,7 +1,7 @@
 pip>=9.0
 numpy>=1.16.0
 scipy>=0.16.1
-scikit-learn>=0.22.0,<0.23  # temp fix: https://github.com/biolab/orange3/pull/4768
+scikit-learn>=0.22.0,!=0.23.0  # 0.23.0 have error with slow k-means, it will be fixed in 0.23.1
 bottleneck>=1.0.0
 # Reading Excel files
 xlrd>=0.9.2