Bump schema salad version for bugfix. (#1069)

Author: tetron

setup.py

@@ -53,7 +53,7 @@
           'ruamel.yaml >= 0.12.4, <= 0.15.77',
           'rdflib >= 4.2.2, < 4.3.0',
           'shellescape >= 3.4.1, < 3.5',
-          'schema-salad >= 4.0, < 5',
+          'schema-salad >= 4.1, < 5',
           'mypy-extensions',
           'six >= 1.9.0',  # >= 1.9.0 required by prov
           'psutil',