docs: update my e-mail

Since anciens.enib.fr has been dead for two months now, without any
hope of recovery, update my e-mail to point to @free.fr instead.

Reported-by: "Bryan Hundven" <bryanhundven@gmail.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
(transplanted from dcdb309b796797d2b4b8ab52a306b91889481db8)

 #!/bin/sh

 set -e

 printf "Running autoconf...\n"

 autoconf -Wall --force

 printf "Done. You may now run:\n    ./configure\n"