Bug 1338216 - Update the ignored directory for mtransport r=jesup

MozReview-Commit-ID: HiXfrMnPkh9

--HG--
extra : rebase_source : 6e18d49dada70abe1fbb202f2d4e280f46b3487f

tools/rewriting/ThirdPartyPaths.txt

@@ -39,7 +39,7 @@ media/libtremor/
 media/libvorbis/
 media/libvpx/
 media/libyuv/
-media/mtransport/
+media/mtransport/third_party/
 media/openmax_dl/
 media/pocketsphinx/
 media/sphinxbase/