Fix a small typo in relay set --help

[anoadragon453]

"inidividual" -> "individual".

Git checklist:

• Describe the change in CHANGELOG.md under the [Unreleased] header.
• Check that commits follow the Mullvad coding guidelines

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This change is 

[faern]

Thanks! We usually don't mention small visual updates in the changelog, it would be way too long otherwise. Could you please remove that part?

[faern]

Thanks for the contribution! Sadly, since I had to rebase to latest master and I'm not able to push to your fork I can't make github understand that it's merged. So I will have to close this. But your commit (minus the changelog entry) is now in the master branch 🎉

[anoadragon453]

Odd, it seems Github has made that option off by default (at least for me). But thanks for getting it in anyways!