[FIX] tools : removing html comments

This commit fixes the malformed comment that would sometimes comment out
the rest of the html resulting in an improper display.

this is due to the new html5 notation --!> not behing understood by
our parser.

this commit replaces any --!> into -->.

this commit also remove  <!--> or <!--->

opw-2812488

closes odoo/odoo#125162

X-original-commit: e3906018
Signed-off-by: Vranckx Florian (flvr) <flvr@odoo.com>