patch 8.2.3605: cannot clear and unlinke a highlight group with hlset()

Problem:    Cannot clear and unlinke a highlight group with hlset() in a
            single call.
Solution:   Add the "force" option. (Yegappan Lakshmanan, closes #9117)
diff --git a/src/testdir/test_vim9_cmd.vim b/src/testdir/test_vim9_cmd.vim
index 9f1cdf1..ee381ed 100644
--- a/src/testdir/test_vim9_cmd.vim
+++ b/src/testdir/test_vim9_cmd.vim
@@ -1570,8 +1570,8 @@
   CheckDefExecAndScriptFailure(lines, 'E486:', 1)
 enddef
 
-" Test for the 'popuppreview' option
-def Test_popuppreview()
+" Test for the 'previewpopup' option
+def Test_previewpopup()
   set previewpopup=height:10,width:60
   pedit Xfile
   var id = popup_findpreview()