fix(material/sort): clear aria description on destroy

Fixes that the sort header wasn't clearing its ARIA description when it gets destroyed, causing a memory leak.

Author: crisbeto

src/material/sort/sort-header.ts

@@ -229,6 +229,7 @@ export class MatSortHeader implements MatSortable, OnDestroy, OnInit, AfterViewI
   ngOnDestroy() {
     this._focusMonitor.stopMonitoring(this._elementRef);
     this._sort.deregister(this);
+    this._ariaDescriber?.removeDescription(this._sortButton, this._sortActionDescription);
     this._rerenderSubscription.unsubscribe();
   }