patch 8.2.1036: popupwin test fails sometimes

Problem:    Popupwin test fails sometimes.
Solution:   Use WaitForAssert() instead of a sleep.

src/testdir/test_popupwin.vim

@@ -2454,9 +2454,11 @@ func Test_popupwin_terminal_buffer()
   call term_sendkeys(termbuf2, "exit\<CR>")
 
   " Exiting shell closes popup window
+  let pupwin = win_getid()
   call feedkeys("exit\<CR>", 'xt')
   " Wait for shell to exit
-  sleep 100m
+  call WaitForAssert({-> assert_notequal(pupwin, win_getid())})
+
   call feedkeys(":quit\<CR>", 'xt')
   call assert_equal(origwin, win_getid())
 endfunc

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1036,
 /**/
     1035,
 /**/