check-code: fix the error message about 'class foo():'

Using 'classs foo():' result in old style object instead of new style object. We
do not want old style object so this check is unrelated to 2.4.

contrib/check-code.py

@@ -234,7 +234,7 b' pypats = ['
      "linebreak after :"),
     (r'class\s[^( \n]+:', "old-style class, use class foo(object)"),
     (r'class\s[^( \n]+\(\):',
-     "class foo() not available in Python 2.4, use class foo(object)"),
+     "class foo() creates old style object, use class foo(object)"),
     (r'\b(%s)\(' % '|'.join(k for k in keyword.kwlist
                             if k not in ('print', 'exec')),
      "Python keyword is not a function"),

tests/test-check-code.t

@@ -115,7 +115,7 b''
    old-style class, use class foo(object)
   ./classstyle.py:7:
    > class empty():
-   class foo() not available in Python 2.4, use class foo(object)
+   class foo() creates old style object, use class foo(object)
   [1]
   $ cat > python3-compat.py << EOF
   > foo <> bar