patch 9.0.1456: shortmess test depends on order of test execution

Problem:    Shortmess test depends on order of test execution.
Solution:   Clear messages. (closes #12264)
diff --git a/src/version.c b/src/version.c
index 50773f8..35c1eea 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1456,
+/**/
     1455,
 /**/
     1454,