Update version in Sphinx API documentation

docs/conf.py

@@ -65,9 +65,9 @@ author = "Donald N. Allingham"
 # built documents.
 #
 # The short X.Y version.
-version = "5.2"
+version = "6.0"
 # The full version, including alpha/beta/rc tags.
-release = "5.2.0"
+release = "6.0.0"
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.