Remove useless option in GCC (pass 1 and final)

In GCC 9.1 release libmpx has been removed.  So --disable-libmpx is no
longer needed.



git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11594 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter05/gcc-pass1.xml

@@ -144,7 +144,6 @@ cd       build</userinput></screen>
     --disable-threads                              \
     --disable-libatomic                            \
     --disable-libgomp                              \
-    --disable-libmpx                               \
     --disable-libquadmath                          \
     --disable-libssp                               \
     --disable-libvtv                               \

chapter06/gcc.xml

@@ -63,7 +63,6 @@ cd       build</userinput></screen>
              --enable-languages=c,c++ \
              --disable-multilib       \
              --disable-bootstrap      \
-             --disable-libmpx         \
              --with-system-zlib</userinput></screen>
 
     <para>Note that for other languages, there are some prerequisites that