patch 8.1.0929: no error when requesting ConPTY but it's not available

Problem:    No error when requesting ConPTY but it's not available.
Solution:   Add an error message. (Hirohito Higashi, closes #3967)
diff --git a/src/version.c b/src/version.c
index 4662831..8a7ab7f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    929,
+/**/
     928,
 /**/
     927,