vm_args.c: rephrase the warning message of keyword argument separation

(old)
test.rb:4: warning: The last argument is used as the keyword parameter
test.rb:1: warning: for `foo' defined here; maybe ** should be added to the call?

(new)
test.rb:4: warning: The last argument is used as keyword parameters; maybe ** should be added to the call
test.rb:1: warning: The called method `foo' is defined here

1 files changed, 1 insertions, 1 deletions

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 8a5aacb42b..57b5075ffd 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -2569,7 +2569,7 @@ rb_scan_args_set(int argc, const VALUE *argv,
                     if (!keyword_given) {
                         /* Warn if treating positional as keyword, as in Ruby 3,
                            this will be an error */
-                        rb_warn("The last argument is used as the keyword parameter");
+                        rb_warn("The last argument is used as keyword parameters");
                     }
                     argc--;
                 }