fix(drag-drop): coerce drop list autoScrollDisabled input

Coerces the `autoScrollDisabled` input to a boolean. Also removes the getter/setter from `sortingDisabled` since we can coerce it before passing it to the drag ref instead.

Fixes angular#17475.

src/cdk/drag-drop/directives/drop-list.ts

@@ -106,11 +106,7 @@ export class CdkDropList<T = any> implements AfterContentInit, OnDestroy {
 
   /** Whether sorting within this drop list is disabled. */
   @Input('cdkDropListSortingDisabled')
-  get sortingDisabled(): boolean { return this._sortingDisabled; }
-  set sortingDisabled(value: boolean) {
-    this._sortingDisabled = coerceBooleanProperty(value);
-  }
-  private _sortingDisabled = false;
+  sortingDisabled: boolean = false;
 
   /**
    * Function that is used to determine whether an item
@@ -276,8 +272,8 @@ export class CdkDropList<T = any> implements AfterContentInit, OnDestroy {
 
       ref.disabled = this.disabled;
       ref.lockAxis = this.lockAxis;
-      ref.sortingDisabled = this.sortingDisabled;
-      ref.autoScrollDisabled = this.autoScrollDisabled;
+      ref.sortingDisabled = coerceBooleanProperty(this.sortingDisabled);
+      ref.autoScrollDisabled = coerceBooleanProperty(this.autoScrollDisabled);
       ref
         .connectedTo(siblings.filter(drop => drop && drop !== this).map(list => list._dropListRef))
         .withOrientation(this.orientation);