Simplify super() calls to Python 3 syntax. (#8344)

This converts calls like super(Foo, self) -> super().

Generated with:

    sed -i "" -Ee 's/super\([^\(]+\)/super()/g' **/*.py

scripts-dev/definitions.py

@@ -11,7 +11,7 @@ import yaml
 
 class DefinitionVisitor(ast.NodeVisitor):
     def __init__(self):
-        super(DefinitionVisitor, self).__init__()
+        super().__init__()
         self.functions = {}
         self.classes = {}
         self.names = {}