patch 8.0.0939: Test_terminal_env is flaky

Problem:    Test_terminal_env is flaky. (James McCoy)
Solution:   Use WaitFor() instead of term_wait().

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    939,
 /**/
     938,
 /**/