Bump mlxtend from 0.17.2 to 0.17.3

Bumps [mlxtend](https://github.com/rasbt/mlxtend) from 0.17.2 to 0.17.3.
- [Release notes](https://github.com/rasbt/mlxtend/releases)
- [Commits](https://github.com/rasbt/mlxtend/compare/v0.17.2...0.17.3)

requirements.txt

@@ -6,8 +6,8 @@ kiwisolver==1.2.0
 importlib-metadata==1.7.0
 joblib==0.16.0
 llvmlite==0.31.0
+mlxtend==0.17.3
 matplotlib==3.3.0
-mlxtend==0.17.2
 more-itertools==8.4.0
 numba==0.48.0
 numpy==1.19.1