[3.13] gh-156614: Fix the parameter list grammar in the language reference (GH-156622) (#156671)

(cherry picked from commit 852381e)

Co-authored-by: Aradhya Gupta <aradhyakb2021@gmail.com>

Author: miss-islington

Doc/reference/compound_stmts.rst

@@ -1227,7 +1227,7 @@ 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` [","]