patch 8.0.1670: terminal window tests are still a bit flaky

Problem:    Terminal window tests are still a bit flaky.
Solution:   Increase the waiting time for the buffer to be created.
diff --git a/src/version.c b/src/version.c
index 813bcfa..59ca7a8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -763,6 +763,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1670,
+/**/
     1669,
 /**/
     1668,