Removed check for texinfo 5.x. Binutils 2.24 and gcc 4.8.2 build with GNU texinfo 5.1

This is for RTEMS Source Builder. Binutils 2.23.x did not build on
Ubuntu 13.10 because of texinfo 5.1. The problem is fixed in
Binutils 2.24, so the check for texinfo 5.x is no longer needed for
this configuration.