refactor(dialog): use gap instead of margins for the action area

Author: desig9stein

projects/igniteui-angular/src/lib/core/styles/components/dialog/_dialog-theme.scss

@@ -180,23 +180,16 @@
         flex-flow: row nowrap;
         justify-content: flex-end;
         padding: $dialog-actions-padding;
+        gap: if($variant == 'indigo', rem(16px), rem(8px));
 
         @if $bootstrap-theme {
             border-top: rem(1px) solid var-get($theme, 'border-color');
         }
 
-        button + button {
-            margin-inline-start: rem(8px);
-        }
-
         @if $variant == 'indigo' {
             .igx-button {
                 --ig-size: 2;
             }
-
-            button + button {
-                margin-inline-start: rem(16px);
-            }
         }
     }
 }