patch 8.2.3543: swapname has double slash when 'directory' ends in it

Problem:    Swapname has double slash when 'directory' ends in double slash.
            (Shane Smith)
Solution:   Remove the superfluous slash. (closes #8876)
diff --git a/src/testdir/test_swap.vim b/src/testdir/test_swap.vim
index 72d204a..143a9af 100644
--- a/src/testdir/test_swap.vim
+++ b/src/testdir/test_swap.vim
@@ -410,7 +410,7 @@
 
   " Check that this also works when 'directory' ends with '//'
   edit Xtestlink
-  call assert_match('Xtestfile\.swp$', s:swapname())
+  call assert_match('Xswapdir[/\\]%.*testdir%Xtestfile\.swp$', s:swapname())
   bwipe!
 
   set dir&