formatting: use nixfmt to format flake.nix

[Jdogzz]

Description of changes

Use nixfmt to format the flake.nix file. As this is just formatting changes I did not check the below boxes.

Things done

• Tested the changes in your own NixOS Configuration
• Tested the changes end-to-end by using your fork of nixos-hardware and
  importing it via <nixos-hardware> or Flake input

[Mic92]

@mergify queue

[mergify]

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🛑 The pull request has been removed from the queue default

The pull request #1108 has been manually updated.

You can take a look at Queue: Embarked in merge queue check runs for more details.

In case of a failure due to a flaky test, you should first retrigger the CI.
Then, re-embark the pull request into the merge queue by posting the comment
@mergifyio refresh on the pull request.

[Mic92]

@mergify queue

[mergify]

queue

🛑 The pull request rule doesn't match anymore

The following conditions don't match anymore:

• -conflict [📌 queue requirement]

[Mic92]

@mergify queue

[mergify]

queue

✅ The pull request has been merged automatically

The pull request has been merged automatically at 166dee4