Update exceptions file with another variant of thread creation memory leak

Since our exceptions match on the stack, they are affected by internal
naming changes, and it looks like a new `ruby_xcalloc_body` function
is now showing up in the stack.

Author: ivoanjo

suppressions/ruby-3.4.supp

@@ -77,3 +77,19 @@
   obj:/usr/bin/tr
   ...
 }
+
+# When a Ruby process forks, it looks like Ruby doesn't clean up the memory of old threads?
+{
+  ruby-native-thread-memory-4
+  Memcheck:Leak
+  fun:calloc
+  fun:calloc1
+  fun:rb_gc_impl_calloc
+  fun:ruby_xcalloc_body
+  fun:ruby_xcalloc
+  fun:native_thread_alloc
+  fun:native_thread_create_dedicated
+  fun:native_thread_create
+  fun:thread_create_core
+  ...
+}