feat(cdk/tree): fix final lint and golden errors

Author: BobobUnicorn

src/cdk/tree/tree.spec.ts

@@ -22,7 +22,6 @@ import {Directionality, Direction} from '@angular/cdk/bidi';
 import {combineLatest, BehaviorSubject, Observable} from 'rxjs';
 import {map} from 'rxjs/operators';
 
-import {BaseTreeControl} from './control/base-tree-control';
 import {TreeControl} from './control/tree-control';
 import {FlatTreeControl} from './control/flat-tree-control';
 import {NestedTreeControl} from './control/nested-tree-control';

tools/public_api_guard/cdk/tree.md

@@ -145,7 +145,6 @@ export class CdkTreeNode<T, K = T> implements FocusableOption, OnDestroy, OnInit
     isExpandable: boolean;
     // (undocumented)
     get isExpanded(): boolean;
-    set isExpanded(isExpanded: boolean);
     // (undocumented)
     get level(): number;
     static mostRecentTreeNode: CdkTreeNode<any> | null;