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.

src/testdir/test_swap.vim

@@ -98,6 +98,9 @@ func Test_missing_dir()
   split bar/x.txt
   only
 
+  " Delete the buffer so that swap file is removed before we try to delete the
+  " directory.  That fails on MS-Windows.
+  %bdelete!
   set directory&
   call delete('Xswapdir', 'rf')
 endfunc

src/version.c

@@ -783,6 +783,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    830,
 /**/
     829,
 /**/