Switch Edge sample tests to Firefox (OSOE-950)

[Piedone]

We continuously had issues with Edge WebDriver downloads (see atata-framework/atata-webdriversetup#16) and one one-two weeks, it's possible that it'll break again (see atata-framework/atata-webdriversetup#18).

We aren't testing anything with Edge per se; we're demonstrating how to run tests with another browser (than Chrome), and a bit testing that behavior too: https://github.com/Lombiq/UI-Testing-Toolbox/blob/dev/Lombiq.Tests.UI.Samples/Tests/MultiBrowserTests.cs and

UI-Testing-Toolbox/Lombiq.Tests.UI.Samples/Tests/BasicVisualVerificationTests.cs

Line 58 in c090875

[Theory, Chrome, Edge]

. For this, we can use FF, there's not much difference, except that under Windows, it's not installed by default. This can be a bit of a hassle if you want to run it locally, but that should be rare, and GHA images of course have it preinstalled anyway.

Jira issue