patch 8.1.0051: MS-Windows: missing #endif

Problem:    MS-Windows: missing #endif.
Solution:   Add the #endif.
diff --git a/src/version.c b/src/version.c
index 29cb801..5ff56fd 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    51,
+/**/
     50,
 /**/
     49,