[4.0] modal buttons rtl (#34856)

This PR fixes a bug with the margin when in rtl that can be seeon in com_templates when you open the modal to create a new file. By switching to logical css properties for the margin it now works correctly in RTL and LTR without any additional classes.

### Before

### After

Author: brianteeman

administrator/templates/atum/scss/blocks/_modals.scss

@@ -4,7 +4,7 @@
 
   .btn {
     padding: 0 22px;
-    margin-right: .5rem;
+    margin-inline-end: .5rem;
     font-size: 1rem;
     line-height: 2.3rem;
     color: var(--template-text-dark);