patch 8.2.3558: Vim9: asserting the wrong variable

Problem:    Vim9: asserting the wrong variable.
Solution:   Don't use Foo, use Goo.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index ae58a0b..7e174df 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1495,7 +1495,7 @@
 
       def DoTest()
         const Goo = G()
-        assert_equal(42, Foo)
+        assert_equal(42, Goo)
       enddef
       DoTest()
   END