How to remove phone validation in invoice block 1.5.6.2

[PrestaShark]

Hi,

I want to remove phone validation in invoice block in order-opc-new-account.tpl because its completely unnecessary data field here. PS 1.5.6.2

<div class="form-group is_customer_param">
	<label for="phone_mobile_invoice" class="col-md-3 control-label text-right"><strong>{l s='Telefon #1'}</strong></label>
		<div class="col-md-9">
			<input type="text" name="phone_mobile_invoice" id="phone_mobile_invoice" value="{if isset($guestInformations) && $guestInformations.phone_mobile_invoice}{$guestInformations.phone_mobile_invoice}{/if}" class="form-control" {if isset($one_phone_at_least) && $one_phone_at_least}required{/if} />
		</div>
</div>	
<div class="form-group is_customer_param">
	<label for="phone_invoice" class="col-md-3 control-label text-right"><strong>{l s='Telefon #1'}</strong></label>
		<div class="col-md-9">
			<input type="text" name="phone_invoice" id="phone_invoice" value="{if isset($guestInformations) && $guestInformations.phone_invoice}{$guestInformations.phone_invoice}{/if}" class="form-control" />
		</div>
</div>														

this bloody part phone_mobile_invoice and phone_invoice

Thanks for any hints

Edited May 6, 2016 by PrestaShark (see edit history)