patch 8.0.1623: terminal kill tests are flaky

Problem:    Terminal kill tests are flaky.
Solution:   Instead of running Vim in a terminal, run it as a normal command.
diff --git a/src/version.c b/src/version.c
index 418ca0c..e647c9b 100644
--- a/src/version.c
+++ b/src/version.c
@@ -767,6 +767,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1623,
+/**/
     1622,
 /**/
     1621,