Remove pthread-win32 from license file (no longer using it)

LICENSE

@@ -71,13 +71,5 @@ The externally maintained libraries used by Node are:
 
   - lib/punycode.js is copyright 2011 Ben Noordhuis and released under the MIT license.
 
-  - deps/pthread-win32/libpthreadGC2.a and
-    deps/pthread-win32/libpthreadGC2d.a is a POSIX threads library for
-    Microsoft Windows and is used for the Windows build and statically
-    linked into the Node executable. This software is freely available at
-    http://sourceware.org/pthreads-win32/ It is Copyright 1998 John E.
-    Bossom and 1999,2006 Pthreads-win32 contributors and licensed under the
-    LGPL. See deps/pthread-win32/COPYING.LIB for more details.
-
   - tools/gyp GYP is a meta-build system copyright 2009 Google Inc and
     licensed under the three clause BSD license. See tools/gyp/LICENSE.