patch 8.1.0254: cannot build on MS-Windows; unused macro HAVE_HANDLE_DROP

Problem:    Cannot build on MS-Windows; Unused macro HAVE_HANDLE_DROP.
Solution:   Adjust #ifdef. Delete the macro.
diff --git a/src/version.c b/src/version.c
index 8b01248..099ea1f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    254,
+/**/
     253,
 /**/
     252,