patch 8.1.2324: with of scrollbar in popup menu not taken into account

Problem:    With of scrollbar in popup menu not taken into account.
Solution:   Add the width of the scrollbar.
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 041d834..8ca7f1c 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -2896,6 +2896,12 @@
   call term_sendkeys(buf, "\<C-N>\<C-N>")
   call VerifyScreenDump(buf, 'Test_popupwin_infopopup_5', {})
 
+  " Test that the popupmenu's scrollbar and infopopup do not overlap
+  call term_sendkeys(buf, "\<Esc>")
+  call term_sendkeys(buf, ":set pumheight=3\<CR>")
+  call term_sendkeys(buf, "cc\<C-X>\<C-U>")
+  call VerifyScreenDump(buf, 'Test_popupwin_infopopup_6', {})
+
   call StopVimInTerminal(buf)
   call delete('XtestInfoPopup')
 endfunc