[FIX] stock: add margin to inventory_at_date button

Steps to reproduce:
- go to inventory report
- remove the "Product > Location" Group by filter.

Problem:
The buttons “Inventory at Date” and “Create” are like merged together because there is no margin right

opw-2721995

closes odoo/odoo#83453

X-original-commit: a33e04df672658c8306a1052b1db79f233f8c54c
Signed-off-by: Arnold Moyaux <arm@odoo.com>
Signed-off-by: Djamel Touati (otd) <otd@odoo.com>

addons/stock/static/src/xml/inventory_report.xml

@@ -3,7 +3,7 @@
 
 <t t-extend="ListView.buttons" t-name="StockInventoryReport.Buttons">
     <t t-jquery="button.o_list_button_discard" t-operation="after">
-        <button class="btn btn-primary o_button_at_date" type="button">
+        <button class="btn btn-primary o_button_at_date mr-2" type="button">
             Inventory at Date
         </button>
     </t>