patch 9.0.0428: autocmd test uses common file name

Problem:    Autocmd test uses common file name.
Solution:   Use unique name to reduce flakiness.
diff --git a/src/version.c b/src/version.c
index dd12a26..4ba0b1e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    428,
+/**/
     427,
 /**/
     426,