3471490: Add layout builder selector for field margin

Closes #3471490

core/themes/olivero/css/components/field.css

@@ -10,7 +10,8 @@
  * Visual styles for fields.
  */
 
-.field:not(:last-child) {
+.field:not(:last-child),
+.layout__region .block-layout-builder:not(:last-child) .field {
   margin-block-end: var(--sp2);
 }