xhtml_style: adjust CSS rule for dialog actions margin

This updates the change to 32cead86 (xhtml_style: set a bottom
margin for dialog action, 2019-05-31) that got impacted by a rule
added on html and body in 5dde17a5 (xhtml_style: make editors in
bottom group use full height, 2022-08-22)

product/ERP5/bootstrap/erp5_xhtml_style/SkinTemplateItem/portal_skins/erp5_xhtml_style/erp5.css.css

@@ -875,7 +875,7 @@ body[dir="rtl"] .logged_in_as {
 }
 
 .bottom_actions {
-  margin-bottom: 1em;
+  padding-bottom: 1em;
 }
 
 .document .actions {