patch 8.2.0242: preview popup window test fails with long directory name

Problem:    Preview popup window test fails with long directory name. (Jakub
            Kądziołka)
Solution:   Use "silent cd". (closes #5615)
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index ad5a808..d331263 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2821,9 +2821,9 @@
   call term_sendkeys(buf, "/another\<CR>\<C-W>}")
   call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_4', {})
 
-  call term_sendkeys(buf, ":cd ..\<CR>:\<CR>")
+  call term_sendkeys(buf, ":silent cd ..\<CR>:\<CR>")
   call VerifyScreenDump(buf, 'Test_popupwin_previewpopup_5', {})
-  call term_sendkeys(buf, ":cd testdir\<CR>")
+  call term_sendkeys(buf, ":silent cd testdir\<CR>")
 
   call term_sendkeys(buf, ":pclose\<CR>")
   call term_sendkeys(buf, ":\<BS>")