patch 8.1.2163: cannot build with +spell but without +syntax

Problem:    Cannot build with +spell but without +syntax.
Solution:   Add #ifdef. (John Marriott)
diff --git a/src/version.c b/src/version.c
index 347e0d5..cfd54a1 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2163,
+/**/
     2162,
 /**/
     2161,