Remove empty section.

Originally committed as revision 7054 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -1275,8 +1275,6 @@ and for a build with shared libraries
 ./configure --enable-mingw32 --enable-memalign-hack --enable-shared --disable-static --extra-cflags=-mno-cygwin --extra-libs=-mno-cygwin
 @end example
 
-@section Mac OS X
-
 @section BeOS
 
 The configure script should guess the configuration itself.