patch 8.1.1896: compiler warning for unused variable

Problem:    Compiler warning for unused variable.
Solution:   Add #ifdef. (John Marriott)  Missing part of 8.1.1892.
diff --git a/src/version.c b/src/version.c
index 2b9a0c6..81e0d5a 100644
--- a/src/version.c
+++ b/src/version.c
@@ -766,6 +766,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1896,
+/**/
     1895,
 /**/
     1894,