patch 8.2.0390: terminal postponed scrollback test is flaky

Problem:    Terminal postponed scrollback test is flaky.
Solution:   Add delay in between sending keys.  Rename dump files.
diff --git a/src/version.c b/src/version.c
index fede5ea..33bdb39 100644
--- a/src/version.c
+++ b/src/version.c
@@ -739,6 +739,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    390,
+/**/
     389,
 /**/
     388,