patch 9.0.1887: Vim9: class members are accessible via object

Problem:  Vim9: class members are accessible via object
Solution: Disable class member variable access using an object

Class methods can be accessed only using the class name and cannot be
accessed using an object. To be consistent with this, do the same for
class member variables also. They can be accessed only using the class
name and not using an object.

closes: #13057

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>
diff --git a/src/vim9class.c b/src/vim9class.c
index 8e2c88b..14d29c7 100644
--- a/src/vim9class.c
+++ b/src/vim9class.c
@@ -1966,8 +1966,7 @@
     {
 	// Search in the object member variable table and the class member
 	// variable table.
-	if (get_member_tv(cl, TRUE, name, len, rettv) == OK
-		|| get_member_tv(cl, FALSE, name, len, rettv) == OK)
+	if (get_member_tv(cl, TRUE, name, len, rettv) == OK)
 	{
 	    *arg = name_end;
 	    return OK;