patch 8.1.2241: match highlight does not combine with 'wincolor'

Problem:    Match highlight does not combine with 'wincolor'.
Solution:   Apply 'wincolor' last on top of any other attribute. (closes #5159)
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 2dcd14d..2c4da0b 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -249,11 +249,12 @@
 	    \ '444 555 666',
 	    \], #{line: 3, col: 10, border: []})
 	set hlsearch
+	hi VeryBlue ctermfg=blue guifg=blue
 	/666
 	call matchadd('ErrorMsg', '111')
-	call matchadd('ErrorMsg', '444')
+	call matchadd('VeryBlue', '444')
 	call win_execute(winid, "call matchadd('ErrorMsg', '111')")
-	call win_execute(winid, "call matchadd('ErrorMsg', '555')")
+	call win_execute(winid, "call matchadd('VeryBlue', '555')")
   END
   call writefile(lines, 'XtestPopupMatches')
   let buf = RunVimInTerminal('-S XtestPopupMatches', #{rows: 10})