Add extra version of py-scikit-learn (#15087)

var/spack/repos/builtin/packages/py-scikit-learn/package.py

@@ -38,6 +38,7 @@ class PyScikitLearn(PythonPackage):
     version('0.21.3', sha256='eb9b8ebf59eddd8b96366428238ab27d05a19e89c5516ce294abc35cea75d003')
     version('0.21.2', sha256='0aafc312a55ebf58073151b9308761a5fcfa45b7f7730cea4b1f066f824c72db')
     version('0.21.1', sha256='228d0611e69e5250946f8cd7bbefec75347950f0ca426d0c518db8f06583f660')
+    version('0.20.3', sha256='c503802a81de18b8b4d40d069f5e363795ee44b1605f38bc104160ca3bfe2c41')
     version('0.20.2', sha256='bc5bc7c7ee2572a1edcb51698a6caf11fae554194aaab9a38105d9ec419f29e6')
     version('0.20.0', sha256='97d1d971f8ec257011e64b7d655df68081dd3097322690afa1a71a1d755f8c18')
     version('0.19.1', sha256='5ca0ad32ee04abe0d4ba02c8d89d501b4e5e0304bdf4d45c2e9875a735b323a0')