patch 8.1.1867: still a timer test that is flaky on Mac

Problem:    Still a timer test that is flaky on Mac.
Solution:   Loop with a sleep instead of one fixed sleep.
diff --git a/src/version.c b/src/version.c
index 4b3637c..a885d9e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1867,
+/**/
     1866,
 /**/
     1865,