style: update button group class for improved layout in NotificationAgents.page and default-base.css

- Changed the class from 'button-group' to 'buttons-spaced' in NotificationAgents.page for better spacing.
- Updated the corresponding CSS class in default-base.css to maintain consistent styling.

emhttp/plugins/dynamix/styles/default-base.css

@@ -198,7 +198,7 @@ a.button,
 
 /* necessary evil until we re-write button styles */
 .buttons-no-margin,
-.button-group {
+.buttons-spaced {
     display: flex;
     flex-wrap: wrap;
     gap: 1.2rem;