patch 8.2.2968: Vim9: memory leak

Problem:    Vim9: memory leak
Solution:   Unreference pt_outer of partial.
diff --git a/src/eval.c b/src/eval.c
index 46d8ca3..b6bee5a 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -4301,6 +4301,9 @@
     else
 	func_ptr_unref(pt->pt_func);
 
+    // "out_up" is no longer used, decrement refcount on partial that owns it.
+    partial_unref(pt->pt_outer.out_up_partial);
+
     // Decrease the reference count for the context of a closure.  If down
     // to the minimum it may be time to free it.
     if (pt->pt_funcstack != NULL)