Fix nokogiri typo

Tod Beardsley · Tod Beardsley · commit 671c0d947343 · 2013-11-26T10:54:31.000-06:00
[SeeRM rapid7#8730]
diff --git a/modules/exploits/windows/fileformat/mswin_tiff_overflow.rb b/modules/exploits/windows/fileformat/mswin_tiff_overflow.rb
@@ -5,7 +5,7 @@
 
 require 'msf/core'
 require 'rex/zip'
-require 'Nokogiri'
+require 'nokogiri'
 
 module ::Nokogiri
 module XML
