remove internal TODO comment

Author: andrewseguin

src/lib/tabs/tab-header.ts

@@ -127,7 +127,6 @@ export class MdTabHeader {
   /**
    * Waits one frame for the view to update, then updates the ink bar and scroll.
    * Note: This must be run outside of the zone or it will create an infinite change detection loop
-   * TODO: internal
    */
   ngAfterViewChecked(): void {
     this._zone.runOutsideAngular(() => {