patch 8.2.0021: timer test fails too often on Travis with MacOS

Problem:    Timer test fails too often on Travis with MacOS.
Solution:   Be less strict with the time.

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    21,
 /**/
     20,
 /**/