nixos/tests: correct comment in radicale.nix (#32574)

The secrets are in fact also stored unhashed, as part of the .drv file
which produces the htpasswd.

nixos/tests/radicale.nix

···
       '';
     };
     # WARNING: DON'T DO THIS IN PRODUCTION!
-    # This puts secrets (albeit hashed) directly into the Nix store for ease of testing.
+    # This puts unhashed secrets directly into the Nix store for ease of testing.
     environment.etc."radicale/htpasswd".source = pkgs.runCommand "htpasswd" {} ''
       ${pkgs.apacheHttpd}/bin/htpasswd -bcB "$out" ${user} ${password}
     '';