[VFS] One more unittest change to fix win10 buildbot

http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-windows10pro-fast/builds/5110
Follow up from r269100.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@269133 91177308-0d34-0410-b5e6-96231b3b80d8

unittests/Basic/VirtualFileSystemTest.cpp

@@ -1085,6 +1085,6 @@ TEST_F(VFSFromYAMLTest, DirectoryIteration) {
   checkContents(O->dir_begin("//root/foo/bar", EC),
                 {"//root/foo/bar/a", "//root/foo/bar/b"});
 
-  checkContents(O->dir_begin("//root/baz", EC),
+  checkContents(O->dir_begin("//root/baz/", EC),
                 {"//root/baz/x", "//root/baz/y", "//root/baz/c"});
 }