patch 8.1.1818: unused variable

Problem:    Unused variable.
Solution:   Remove the variable. (Mike Williams)
diff --git a/src/version.c b/src/version.c
index 287775f..8537df1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -774,6 +774,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1818,
+/**/
     1817,
 /**/
     1816,