Fix missing paren.

Doc/api/newtypes.tex

@@ -854,7 +854,7 @@ PyMappingMethods *tp_as_mapping;
     GC-related fields \member{tp_traverse} and \member{tp_clear} are
     present in the type object; but those fields also exist when
     \constant{Py_TPFLAGS_HAVE_GC} is clear but
-    \constant{Py_TPFLAGS_HAVE_RICHCOMPARE} is set).
+    \constant{Py_TPFLAGS_HAVE_RICHCOMPARE} is set.
   \end{datadesc}
 
   \begin{datadesc}{Py_TPFLAGS_DEFAULT}