gh-156614: Fix function parameter grammar in documentation

Author: challenge456

Doc/reference/compound_stmts.rst

@@ -1235,7 +1235,7 @@ A function definition defines a user-defined function object (see section
                  :   | `parameter_list_no_posonly`
    parameter_list_no_posonly: `defparameter` ("," `defparameter`)* ["," [`parameter_list_starargs`]]
                             : | `parameter_list_starargs`
-   parameter_list_starargs: "*" [`star_parameter`] ("," `defparameter`)* ["," [`parameter_star_kwargs`]]
+   parameter_list_starargs: "*" `star_parameter` ("," `defparameter`)* ["," [`parameter_star_kwargs`]]
                           : | "*" ("," `defparameter`)+ ["," [`parameter_star_kwargs`]]
                           : | `parameter_star_kwargs`
    parameter_star_kwargs: "**" `parameter` [","]