gh-117764: Add signature for functools.partial() (GH-117775)

Author: serhiy-storchaka

Modules/_functoolsmodule.c

@@ -335,8 +335,9 @@ partial_call(partialobject *pto, PyObject *args, PyObject *kwargs)
 }
 
 PyDoc_STRVAR(partial_doc,
-"partial(func, *args, **keywords) - new function with partial application\n\
-    of the given arguments and keywords.\n");
+"partial(func, /, *args, **keywords)\n--\n\n\
+Create a new function with partial application of the given arguments\n\
+and keywords.");
 
 #define OFF(x) offsetof(partialobject, x)
 static PyMemberDef partial_memberlist[] = {