Remove Ajax fix for pre Firefox 1.5

Fuse does not support Firefox versions before 1.5
we should remove this chunk of code in the Fuse.Ajax.Request.

/* Force "Connection: close" for older Mozilla browsers to work
 * around a bug where XMLHttpRequest sends an incorrect
 * Content-length header. See Mozilla Bugzilla #246651.
 */
 if (this.transport.overrideMimeType &&
    (userAgent.match(/Gecko\/(\d{4})/) || [0,2005])[1] < 2005)
   headers['Connection'] = 'close';

I have been reading and it apparently causes issues with http authentication as well.

http://dev.rubyonrails.org/ticket/5809

http://groups.google.com/group/jquery-en/browse_thread/thread/8ff37a5c8660f4ec