Remove duplicate values for autocapitalize (#590)

src/components/textarea/textarea.ts

@@ -97,12 +97,6 @@ export default class SlTextarea extends LitElement {
 
   /** The textarea's autocaptialize attribute. */
   @property() autocapitalize:
-    | 'off'
-    | 'none'
-    | 'on'
-    | 'sentences'
-    | 'words'
-    | 'characters'
     | 'off'
     | 'none'
     | 'on'