fix bad merge

Author: zarend

src/dev-app/tree/tree-demo.html

@@ -27,10 +27,6 @@
     <mat-expansion-panel-header>CDK Nested tree (levelAccessor)</mat-expansion-panel-header>
     <cdk-tree-nested-level-accessor-example></cdk-tree-nested-level-accessor-example>
   </mat-expansion-panel>
-  <mat-expansion-panel>
-    <mat-expansion-panel-header>Todo list tree</mat-expansion-panel-header>
-    <tree-checklist-example></tree-checklist-example>
-  </mat-expansion-panel>
   <mat-expansion-panel>
     <mat-expansion-panel-header>Dynamic flat tree</mat-expansion-panel-header>
     <tree-dynamic-example></tree-dynamic-example>