"[REVERT][FIX] point_of_sale: field date of report.pos.order should be a datetime"

This reverts commit 97d097a2af8c3992d5108bd75b82fa8479d196cc.

As explained in the commit comments (on Github), this patch leads to an infinite loop in 7.0, the filter of the pos orders report using the '=' operator in its domain, which is not available for datetime fields, but is for date fields.

This should not be forward ported to newer release (saas-3)