patch 8.2.5107: some callers of rettv_list_alloc() check for not OK

Problem:    Some callers of rettv_list_alloc() check for not OK. (Christ van
            Willegen)
Solution:   Use "==" instead of "!=" when checking the return value.
diff --git a/src/insexpand.c b/src/insexpand.c
index 20df1b0..4a5feac 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -3089,7 +3089,7 @@
 {
     list_T	*what_list = NULL;
 
-    if (rettv_dict_alloc(rettv) != OK)
+    if (rettv_dict_alloc(rettv) == FAIL)
 	return;
 
     if (in_vim9script() && check_for_opt_list_arg(argvars, 0) == FAIL)