String change as part of dialog cleanup, b=158881, r=brade, sr=alecf

editor/ui/dialogs/locale/en-US/EdLinkChecker.dtd

@@ -25,4 +25,6 @@
 <!ENTITY windowTitle.label     "Check Image and Link Locations">
 <!ENTITY urlsNotFound.label    "The following image or link locations were not found:">
 <!ENTITY notFoundKey.label     "(&quot;X&quot; = file not found, &quot;?&quot; = timed-out attempting to connect.)">
-<!ENTITY changeUrlButton.label "Change Location of Selected Item">
+<!ENTITY changeUrlButton.label "Change Location of Selected Item">
+<!ENTITY succeeded.label       "Succeeded">
+<!ENTITY failed.label          "Failed">