sed.cpp: Change long option name to GNU equivalent

GNU sed uses --regexp-extended not --regex-extended

Author: cofinalsubnets

Userland/Utilities/sed.cpp

@@ -1047,7 +1047,7 @@ ErrorOr<int> serenity_main(Main::Arguments args)
             return true;
         },
     });
-    arg_parser.add_ignored("regex-extended", 'E');
+    arg_parser.add_ignored("regexp-extended", 'E');
     arg_parser.add_option(strict_posix, "Use POSIX regular expressions", "posix", 'p');
     arg_parser.add_option(edit_in_place, "Edit file in place, implies -n", "in-place", 'i');
     arg_parser.add_positional_argument(pos_args, "script and/or file", "...", Core::ArgsParser::Required::No);