patch 8.2.0829: filter() may give misleading error message

Problem:    filter() may give misleading error message.
Solution:   Also mention Blob as an allowed argument.
diff --git a/src/list.c b/src/list.c
index b9e7e34..7c06cfc 100644
--- a/src/list.c
+++ b/src/list.c
@@ -1768,7 +1768,7 @@
     }
     else
     {
-	semsg(_(e_listdictarg), ermsg);
+	semsg(_(e_listdictblobarg), ermsg);
 	return;
     }