[REF] web: remove useless oe_number rule

This was introduced as a fix for grouped list views' headers while we
should have added the 'o_list_number' class instead... which is the
case now. So the oe_number rule became useless.

See https://github.com/odoo/enterprise/commit/a2ce226a2a085b26174cdfd32922517dff39658c
See https://github.com/odoo/odoo/commit/5d13a2f431e1c96e075b04d0eb07d98b912a6547
See https://github.com/odoo/odoo/pull/23966

addons/web/static/src/less/list_view.less

@@ -109,9 +109,6 @@
                 }
             }
         }
-        > td.oe_number{
-            text-align: right;
-        }
     }
     tbody + tbody {
         border-top: none;  // Override bootstrap for grouped list views