patch 8.0.0939: Test_terminal_env is flaky

Problem:    Test_terminal_env is flaky. (James McCoy)
Solution:   Use WaitFor() instead of term_wait().
diff --git a/src/version.c b/src/version.c
index a8b07dc..4978e87 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    939,
+/**/
     938,
 /**/
     937,