patch 8.1.2089: do not get a hint that $TEST_FILTER was active

Problem:    Do not get a hint that $TEST_FILTER was active.
Solution:   Mention $TEST_FILTER if no functions were executed.
diff --git a/src/version.c b/src/version.c
index 35253eb..552f82a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -758,6 +758,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2089,
+/**/
     2088,
 /**/
     2087,