[FIX] website_slides: fix buy now course button

When one customize a course by adding the 'buy now'
button. Both the 'Add to cart' and 'Buy now' button
doesn't fill the container width.
This commit fix this by changing 'btn-block' class
by 'd-block'.
See commit eee625bb

Task-3299234

closes odoo/odoo#120394

Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/website_sale_slides/views/website_slides_templates.xml

@@ -150,13 +150,13 @@
 <template name="Display 'Buy Now'" id="course_option_buy_course_now" inherit_id="website_sale_slides.course_buy_course_button" active="False">
     <xpath expr="//div[hasclass('add_to_cart_button')]" position="before">
         <div class="mb-1">
-            <a role="button" class="post_link btn btn-primary btn-block" t-attf-href="/shop/cart/update?product_id={{channel.product_id.id}}&amp;express=1">
+            <a role="button" class="post_link btn btn-primary d-block" t-attf-href="/shop/cart/update?product_id={{channel.product_id.id}}&amp;express=1">
                 <i class="fa fa-bolt"></i> Buy Now
             </a>
         </div>
     </xpath>
     <xpath expr="//div[hasclass('add_to_cart_button')]//a[@id='add_to_cart']" position="attributes">
-        <attribute name="class">btn btn-outline-primary btn-block js_check_product o_js_add_to_cart a-submit</attribute>
+        <attribute name="class">btn btn-outline-primary d-block js_check_product o_js_add_to_cart a-submit</attribute>
     </xpath>
 </template>