Add missing .js extension on import from mwc-snackbar to lit-html/directive

PiperOrigin-RevId: 397522675

Author: aomarks

packages/snackbar/accessible-snackbar-label-directive.ts

@@ -10,7 +10,7 @@
 import MDCSnackbarFoundation from '@material/snackbar/foundation';
 import {html, render, TemplateResult} from 'lit-html';
 import {AsyncDirective} from 'lit-html/async-directive.js';
-import {ChildPart, directive, DirectiveParameters, PartInfo, PartType} from 'lit-html/directive';
+import {ChildPart, directive, DirectiveParameters, PartInfo, PartType} from 'lit-html/directive.js';
 
 const {ARIA_LIVE_DELAY_MS} = MDCSnackbarFoundation.numbers;
 /**