test: move app-layout styles import to avoid warning with Lit

[web-padawan]

Description

This fixes the following warning introduced in #8387:

packages/app-layout/test/app-layout-lit.test.js:

 🚧 Browser logs:
      The custom element definition for "vaadin-app-layout" was finalized before a style module was registered. Ideally, import component specific style modules before importing the corresponding custom element. This warning can be suppressed by setting "window.Vaadin.suppressPostFinalizeStylesWarning = true".

Type of change

• Test

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[vaadin-bot]

This ticket/PR has been released with Vaadin 24.7.0.alpha3 and is also targeting the upcoming stable 24.7.0 version.