[forms] Fix HTableFormRenderer _render_fields method behavior when display_label is False. Indeed, now the extra <tr><th>...</th></tr> are not inserted anymore unless display_label is True. Closes #3811325.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances