feat(accordion): allow intermediate elements between accordion and expansion panel pt2

Author: josephperrott

src/lib/expansion/expansion-panel.ts

@@ -88,7 +88,7 @@ export class MatExpansionPanel extends CdkAccordionItem
   /** ID for the associated header element. Used for a11y labelling. */
   _headerId = `mat-expansion-panel-header-${uniqueId++}`;
 
-  constructor(@Optional() @Host() accordion: MatAccordion,
+  constructor(@Optional() accordion: MatAccordion,
               _changeDetectorRef: ChangeDetectorRef,
               _uniqueSelectionDispatcher: UniqueSelectionDispatcher,
               private _viewContainerRef: ViewContainerRef) {