patch 8.1.0291: 'incsearch' highlighting not used for :sort

Problem:    'incsearch' highlighting not used for :sort.
Solution:   Handle pattern in :sort command.
diff --git a/src/version.c b/src/version.c
index 279908e..56ab418 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    291,
+/**/
     290,
 /**/
     289,