patch 8.2.0978: leaking memory in termcodes test

Problem:    Leaking memory in termcodes test.
Solution:   Set t_8u with set_option_value().

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    978,
 /**/
     977,
 /**/