web: migrate to lit 2

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

web/src/elements/LoadingOverlay.ts

@@ -1,14 +1,7 @@
-import {
-    css,
-    CSSResult,
-    customElement,
-    html,
-    LitElement,
-    property,
-    TemplateResult,
-} from "lit-element";
+import { css, CSSResult, html, LitElement, TemplateResult } from "lit";
 import PFBase from "@patternfly/patternfly/patternfly-base.css";
 import { PFSize } from "./Spinner";
+import { customElement, property } from "lit/decorators";
 
 @customElement("ak-loading-overlay")
 export class LoadingOverlay extends LitElement {