Bug 1673959 - Port extra strings from |Bug 1425962 - Subscribe dialog broken...

Bug 1673959 - Port extra strings from |Bug 1425962 - Subscribe dialog broken for IMAP and news| and |Bug 1466705 - Fix subscribe dialog for IMAP and news| - bug 1425962 part. r=frg a=frg

suite/locales/en-US/chrome/mailnews/subscribe.properties

 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
-columnHeader-nntp=Newsgroup name
-columnHeader-imap=Folder name
+subscribeLabel-nntp=Select the newsgroups to subscribe to:
+subscribeLabel-imap=Select the folders to subscribe to:
 currentListTab-nntp.label=Current Group List
 currentListTab-nntp.accesskey=L
 currentListTab-imap.label=Folder List