Fix unbound method optimization for static types.

Cython/Compiler/ExprNodes.py

@@ -5324,6 +5324,9 @@ class AttributeNode(ExprNode):
                     # as an ordinary function.
                     if entry.func_cname:
                         cname = entry.func_cname
+                        if entry.type.is_static_method:
+                            ctype = entry.type
+                        else:
                             # Fix self type.
                             ctype = copy.copy(entry.type)
                             ctype.args = ctype.args[:]