pythongh-131457: Fix typo in BNF description of function signatures (python#131460)

Author: srinivasreddy

Doc/reference/compound_stmts.rst

@@ -1222,7 +1222,7 @@ A function definition defines a user-defined function object (see section
    parameter_list_no_posonly: `defparameter` ("," `defparameter`)* ["," [`parameter_list_starargs`]]
                             : | `parameter_list_starargs`
    parameter_list_starargs: "*" [`star_parameter`] ("," `defparameter`)* ["," [`parameter_star_kwargs`]]
-                          : "*" ("," `defparameter`)+ ["," [`parameter_star_kwargs`]]
+                          : | "*" ("," `defparameter`)+ ["," [`parameter_star_kwargs`]]
                           : | `parameter_star_kwargs`
    parameter_star_kwargs: "**" `parameter` [","]
    parameter: `identifier` [":" `expression`]