patch 8.1.2168: heredoc assignment not skipped in if block

Problem:    Heredoc assignment not skipped in if block.
Solution:   Check if "skip" is set. (closes #5063)
diff --git a/src/version.c b/src/version.c
index 3bcd910..4f0e6fa 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2168,
+/**/
     2167,
 /**/
     2166,