chore: fix linting errors (#6044)

Fixes a couple of linting errors that were introduced in master.

src/lib/table/cell.ts

@@ -12,7 +12,7 @@ import {
   CdkCellDef,
   CdkColumnDef,
   CdkHeaderCell,
-  CdkHeaderCellDef
+  CdkHeaderCellDef,
 } from '@angular/cdk/table';
 
 /** Workaround for https://github.com/angular/angular/issues/17849 */

src/lib/table/row.ts

@@ -12,7 +12,7 @@ import {
   CdkRow,
   CDK_ROW_TEMPLATE,
   CdkRowDef,
-  CdkHeaderRowDef
+  CdkHeaderRowDef,
 } from '@angular/cdk/table';
 
 /** Workaround for https://github.com/angular/angular/issues/17849 */

tools/dashboard/src/app/dashboard-app.ts

@@ -1,5 +1,9 @@
 import {Component} from '@angular/core';
 import {AngularFireDatabase, FirebaseListObservable} from 'angularfire2/database';
+
+// This import is only used to define a generic type. The current TypeScript version incorrectly
+// considers such imports as unused (https://github.com/Microsoft/TypeScript/issues/14953)
+// tslint:disable-next-line:no-unused-variable
 import {PayloadResult, CoverageResult} from './data-definitions';
 
 @Component({