Fix request #7372: Radio button: useless none value

There is no need to display a "None" option for a group of radio button
that is required.

It is now removed from submit, update and admin view.

Change-Id: I2eedc11c76580d0261299992d1e50d9822bad330
Merge commit 'refs/changes/22/2922/3' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #7372: Radio button: useless none value

Change-Id: Ie9e5fac220d15059bbb95139d81365e20d63e7b5
This is Tuleap 7.4.99.9

Change-Id: I7d372e4a7471619351eb7d22a4927ea6c147d8dc