patch 8.1.0280: 'incsearch' highlighting does not work for ":g!/"

Problem:    'incsearch' highlighting does not work for ":g!/".
Solution:   Skip the exclamation mark. (Hirohito Higashi)
diff --git a/src/version.c b/src/version.c
index 4a9dd14..1450992 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    280,
+/**/
     279,
 /**/
     278,