configure: s/don't/do not/

The autoconf manual suggests not to use ' in messages.

I don't why they do, but it breaks syntax-highlighting.

Just remove the lone quote we have.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

 # Compute s390-specific values

 CT_DoArchTupleValues() {

     # That's the only thing to override

     if [ "${CT_ARCH_64}" = "y" ]; then

         CT_TARGET_ARCH="s390x${CT_ARCH_SUFFIX}"

     fi

 }