followup fix for "tdf#109269 very slow loading of user-defined dictionary"

i.e. commit 3b1f5ce3a37b09880b63f829bc0a349075fb6245

Change-Id: Ic03c9518fec2ca066bf31272cddd611b05c4773b
Reviewed-on: https://gerrit.libreoffice.org/56391
Tested-by: Jenkins
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>

cui/source/options/optdict.cxx

@@ -542,7 +542,7 @@ void SvxEditDictionaryDialog::ShowWords_Impl( sal_uInt16 nId )
     {
         pWordsLB->InsertEntry(rStr, nullptr, false, TREELIST_APPEND);
     }
-    pWordsLB->SetUpdateMode(false);
+    pWordsLB->SetUpdateMode(true);
 
     if (pWordsLB->GetEntryCount())
     {