patch 9.0.1831: Vim9: failing null test

Problem:  Vim9: failing null test
Solution: Use required public keyword

closes: #12982

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Gianmaria Bajo <mg1979.git@gmail.com>
diff --git a/src/testdir/test_vim9_class.vim b/src/testdir/test_vim9_class.vim
index c859ee4..127531d 100644
--- a/src/testdir/test_vim9_class.vim
+++ b/src/testdir/test_vim9_class.vim
@@ -1184,7 +1184,7 @@
   lines =<< trim END
     vim9script
     class A
-        this.val: string
+        public this.val: string
     endclass
 
     def F()
@@ -1214,7 +1214,7 @@
   lines =<< trim END
     vim9script
     class A
-        this.val: string
+        public this.val: string
     endclass
 
     var obj: A