patch 8.2.0575: :digraph! not tested

Problem:    :digraph! not tested.
Solution:   Add a test. (Dominique Pelle, closes #5925)
diff --git a/src/version.c b/src/version.c
index 3bb9479..0705e75 100644
--- a/src/version.c
+++ b/src/version.c
@@ -747,6 +747,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    575,
+/**/
     574,
 /**/
     573,