fix!: remove fixed width from middle position

vaadin/vaadin-notification#126

Author: jouni

packages/vaadin-notification/theme/lumo/vaadin-notification-styles.js

@@ -40,7 +40,6 @@ registerStyles(
     }
 
     :host([slot^='middle']) {
-      width: 20em;
       max-width: 80vw;
       margin: var(--lumo-space-s) auto;
     }