remove dead code. #92960. rs=mscott

mailnews/base/resources/locale/en-US/messenger.dtd

@@ -481,10 +481,3 @@ Rights Reserved.
 <!-- Print Engine -->
 <!ENTITY printEngine.title "Printing...">
 
-<!-- Open/Save Attachment -->
-<!ENTITY openSaveAttachment.title "Open/Save Attachment">
-<!ENTITY openSaveAttachmentHeading.label "Attachment: ">
-<!ENTITY openSaveAttachmentWarning.label "Some files can contain viruses or otherwise be harmful to your computer. It is important to be certain that this file is from a trustworthy source.">
-<!ENTITY openSaveAttachmentToDo.label "What would you like to do with this file?">
-<!ENTITY openSaveAttachmentOpen.label "Open it">
-<!ENTITY openSaveAttachmentSave.label "Save it to disk">