patch 8.2.0747: cannot forcefully close all popups

Problem:    Cannot forcefully close all popups.
Solution:   Add the "force" argument to popup_clear().  Use it after running a
            test.  Put back the check for a popup when editing a file.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index 13d4784..b9d85f4 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -188,9 +188,9 @@
   au!
   au SwapExists * call HandleSwapExists()
 
-  " Close any stray popup windows
+  " Close any stray popup windows.
   if has('popupwin')
-    call popup_clear()
+    call popup_clear(1)
   endif
 
   " Close any extra tab pages and windows and make the current one not modified.