use normal accessible button, which is themed

res/css/views/rooms/_RoomRecoveryReminder.scss

@@ -33,11 +33,6 @@ limitations under the License.
     margin-bottom: 1em;
 }
 
-.mx_RoomRecoveryReminder_button {
-    @mixin mx_DialogButton;
-    margin: 0 10px;
-}
-
 .mx_RoomRecoveryReminder_secondary {
     font-size: 90%;
     margin-top: 1em;

src/components/views/rooms/RoomRecoveryReminder.js

@@ -150,7 +150,7 @@ export default class RoomRecoveryReminder extends React.PureComponent {
                     )}</p>
                 </div>
                 <div className="mx_RoomRecoveryReminder_buttons">
-                    <AccessibleButton className="mx_RoomRecoveryReminder_button"
+                    <AccessibleButton kind="primary"
                         onClick={this.onSetupClick}>
                         {setupCaption}
                     </AccessibleButton>