docs(material/expansion): Fix expansion-expand-collapse-all-example selector (#19499)

Author: rnlee0054

src/components-examples/material/expansion/expansion-expand-collapse-all/expansion-expand-collapse-all-example.ts

@@ -5,7 +5,7 @@ import {MatAccordion} from '@angular/material/expansion';
  * @title Accordion with expand/collapse all toggles
  */
 @Component({
-  selector: 'expansion-toggle-all-example',
+  selector: 'expansion-expand-collapse-all-example',
   templateUrl: 'expansion-expand-collapse-all-example.html',
   styleUrls: ['expansion-expand-collapse-all-example.css'],
 })