modify pymanopt version in requirements

Mokhtar Z. Alaya · Mokhtar Z. Alaya · commit c5b1c7cfa3bb · 2020-01-24T09:23:02.000+01:00
diff --git a/requirements.txt b/requirements.txt
@@ -4,6 +4,7 @@ cython
 matplotlib
 sphinx-gallery
 autograd
-pymanopt
+pymanopt== 0.2.4, python_version < '3'
+pymanopt, python_version >= '3'
 cvxopt
 pytest
