Playwright test don't work for electron with npm build

[tsmaeder]

Bug Description:

In eclipse-theia/theia-e2e-test-suite#44, our performance tests don't work for Electron. This is due to the electron package being hosted to a different location than with yarn.

Steps to Reproduce:

1. go to examples/playwright
2. run 'npm run ui-tests-electron'
3. observe: none of the tests work.

Additional Information

• Operating System: Windows
• Theia Version: 1.57 master