Fix the string resource used to indicate MHTML save type

BUG=369875
TEST=On a Chromebook, try to save a web page and see the file type selector.

Review URL: https://codereview.chromium.org/287083004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270955 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/generated_resources.grd

@@ -11481,8 +11481,8 @@ The following application will be launched if you accept this request:
       <message name="IDS_SAVE_PAGE_DESC_HTML_ONLY" desc="In the Save Page dialog, the description of saving only the HTML of a webpage.">
         Webpage, HTML Only
       </message>
-      <message name="IDS_SAVE_PAGE_DESC_SINGLE_FILE" desc="In the Save Page dialog, the description of saving both the HTML and all shown resources into an archive.">
-        Web Archive, Single File
+      <message name="IDS_SAVE_PAGE_DESC_SINGLE_FILE" desc="In the Save Page dialog, the description of saving both the HTML and all shown resources into a single file.">
+        Webpage, Single File
       </message>
       <message name="IDS_SAVE_PAGE_DESC_COMPLETE" desc="In the Save Page dialog, the description of saving both the HTML and all shown resources.">
         Webpage, Complete