fix(python-generator): make signatures compliant with PEP 8

The '=' character at a parameter in the signature was surrounded with
spaces previously. That is no longer the case, unless there is a type
hint.

src/jcloud_docsgen/core/python/arguments.py

@@ -142,6 +142,9 @@ class PythonFunctionArgument:
             str_repr += ': ' + self.annotation
 
         if self.default is not None:
+            if self.annotation is None:
+                str_repr += '=' + self.default
+            else:
                 str_repr += ' = ' + self.default
 
         return str_repr