fix types around sending stickers

src/components/structures/RoomView.tsx

@@ -1196,7 +1196,7 @@ export default class RoomView extends React.Component<IProps, IState> {
         });
     };
 
-    private injectSticker(url, info, text) {
+    private injectSticker(url: string, info: object, text: string) {
         if (this.context.isGuest()) {
             dis.dispatch({action: 'require_registration'});
             return;