patch 8.1.0767: when deleting lines at the bottom signs are misplaced

Problem:    When deleting lines at the bottom signs are misplaced.
Solution:   Properly update the line number of signs at the end of a buffer
            after a delete/undo operation. (Yegappan Lakshmanan, closes #3798)
diff --git a/src/version.c b/src/version.c
index 4e3c5a2..719fd07 100644
--- a/src/version.c
+++ b/src/version.c
@@ -792,6 +792,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    767,
+/**/
     766,
 /**/
     765,