patch 8.1.1675: listener list not correctly updated on listener_remove()

Problem:    Listener list not correctly updated on listener_remove().
Solution:   Only set "prev" when not removing a listener.  Return one if the
            listener was found and removed.
diff --git a/src/version.c b/src/version.c
index 04a2e68..7e3c180 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1675,
+/**/
     1674,
 /**/
     1673,