Use the fixed API on the mediawiki exploit

lib/rex/mime/message.rb

@@ -130,7 +130,6 @@ class Message
 
     self.parts.each do |part|
       msg << force_crlf("--" + self.bound + "\r\n")
-      #msg << part.to_s + "\r\n"
       msg << force_crlf(part.header.to_s + "\r\n")
       msg << part.content + "\r\n"
     end

modules/exploits/multi/http/mediawiki_thumb.rb

@@ -283,7 +283,7 @@ class Metasploit3 < Msf::Exploit::Remote
     upload_mime.add_part(title, nil, nil, "form-data; name=\"title\"")
     upload_mime.add_part("1", nil, nil, "form-data; name=\"wpDestFileWarningAck\"")
     upload_mime.add_part(wp_upload, nil, nil, "form-data; name=\"wpUpload\"")
-    post_data = upload_mime.to_s(true)
+    post_data = upload_mime.to_s
 
     print_status("Uploading DjVu file #{file_name}...")