patch 8.1.0830: test leaves directory behind on MS-Windows

Problem:    Test leaves directory behind on MS-Windows.
Solution:   Close buffer before deleting directory.
diff --git a/src/version.c b/src/version.c
index af28903..9891796 100644
--- a/src/version.c
+++ b/src/version.c
@@ -784,6 +784,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    830,
+/**/
     829,
 /**/
     828,