k3s.tests: fix eval

[numinit]

The k3s tests depend on everything in nixosTests.k3s, which depend on all the k3s versions using tryEval. Just delete the recurseIntoAttrs to prevent this error:

$ nix-instantiate -A k3s.tests
error:
       … while evaluating the attribute 'recurseForDerivations'

       … while selecting an attribute
         at pkgs/applications/networking/cluster/k3s/builder.nix:487:36:
          486|         in
          487|         lib.mapAttrs (name: value: nixosTests.k3s.${name}.${k3s_version}) nixosTests.k3s;
             |                                    ^
          488|       tests = passthru.mkTests k3sVersion;

       error: expected a set but found a Boolean: true

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• Nixpkgs 25.11 Release Notes (or backporting 24.11 and 25.05 Nixpkgs Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
• NixOS 25.11 Release Notes (or backporting 24.11 and 25.05 NixOS Release notes)
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[nixpkgs-ci]

Successfully created backport PR for release-25.05:

• [Backport release-25.05] k3s.tests: fix eval #412769