patch 8.2.0446: listener with undo of deleting all lines not tested

Problem:    Listener with undo of deleting all lines not tested.
Solution:   Add a test.
diff --git a/src/version.c b/src/version.c
index f99097d..6b5e252 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    446,
+/**/
     445,
 /**/
     444,