[Bug #19081] Show the caller location in warning for Ractor

The internal location in ractor.rb is not usefull at all.
```
$ ruby -e 'Ractor.new {}'
<internal:ractor>:267: warning: Ractor is experimental, ...
```

1 files changed, 0 insertions, 6 deletions

diff --git a/ractor.c b/ractor.c
index 7fea312ab0..3569202e58 100644
--- a/ractor.c
+++ b/ractor.c
@@ -1438,12 +1438,6 @@ cancel_single_ractor_mode(void)
     }
 
     ruby_single_main_ractor = NULL;
-
-    if (rb_warning_category_enabled_p(RB_WARN_CATEGORY_EXPERIMENTAL)) {
-        rb_category_warn(RB_WARN_CATEGORY_EXPERIMENTAL,
-                         "Ractor is experimental, and the behavior may change in future versions of Ruby! "
-                         "Also there are many implementation issues.");
-    }
 }
 
 static void