add delete language test

[jemayn]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes

Description

The test creates a few languages through the API, then goes through UI to delete one of them.

This was demoed and worked on with all participants at the Umbraco London Meetup tonight.
Special thanks to @warrenbuckley @ravimotha @deanleigh for help debugging 🙂

[umbrabot]

Hi there @jemayn, thank you for this contribution! 👍

While we wait for one of the Core Collaborators team to have a look at your work, we wanted to let you know about that we have a checklist for some of the things we will consider during review:

• It's clear what problem this is solving, there's a connected issue or a description of what the changes do and how to test them
• The automated tests all pass (see "Checks" tab on this PR)
• The level of security for this contribution is the same or improved
• The level of performance for this contribution is the same or improved
• Avoids creating breaking changes; note that behavioral changes might also be perceived as breaking
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[nul800sebastiaan]

Great work once again @jemayn - works as advertised, thanks very much! ⭐

[jemayn]

Hey @nul800sebastiaan

Thanks! I think we may need to fix this merge slightly though. Seems that during the time it has been open the test folder has moved, so now these files are committed in the wrong place 😊

I will try to fix it up during the hackathon on Friday if nothing has been done before then.

[nul800sebastiaan]

Cherry picked for v8 in 427c85e