[FIX] web, website_sale: add missing `.float-start class

Commit[1] aimed to fix a layout issue inside the eCommerce categories
form view on mobile devices.

Prior to Commit[1], a `.float-start` class was applied to the content
of thesheet, moving it "out of the flow", resulting in a wrong sized
form_sheet.

To fix the issue, we removed the `.float-start` class, but doing such
a change introduced a risk for users's customizations.

======
After
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To prevent this issue, we reintroduce the initial lines, and will provide
a fix in another PR.

Commit[1]: 9837396
Related to task-3847917

closes odoo/odoo#160858

X-original-commit: 0914a0bd179a6b644e51de25bfad0555ea0f40ca
Signed-off-by: Pierre Paridans (app) <app@odoo.com>
Signed-off-by: Chrysanthe Gomrée (chgo) <chgo@odoo.com>

addons/website_sale/views/product_views.xml

@@ -228,8 +228,8 @@
             <form string="Website Public Categories">
                 <sheet>
                     <field name="image_1920" widget="image" class="oe_avatar" options="{'preview_image': 'image_128'}"/>
-                    <div>
-                        <group class="col-md-4 col-lg-6 pe-3">
+                    <div class="float-start">
+                        <group>
                             <field name="name"/>
                             <field name="parent_id"/>
                             <field name="website_id" options="{'no_create': True}" groups="website.group_multi_website"/>