patch 8.1.1780: warning for file no longer available is repeated

Problem:    Warning for file no longer available is repeated every time Vim is
            focused. (Brian Armstrong)
Solution:   Only give the message once. (closes #4748)
diff --git a/src/version.c b/src/version.c
index 463456b..15577e0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1780,
+/**/
     1779,
 /**/
     1778,