check-meta: Fix typos in comment and error message

  isMarkedInsecure = attrs: (attrs.meta.knownVulnerabilities or [ ]) != [ ];

  # Alow granular checks to allow only some unfree packages

  # Allow granular checks to allow only some unfree packages

  # Example:

  # {pkgs, ...}:

  # {

      however ${getNameWithVersion attrs} only has the outputs: ${builtins.concatStringsSep ", " actualOutputs}

      and is missing the following ouputs:

      and is missing the following outputs:

      ${concatStrings (builtins.map (output: "  - ${output}\n") missingOutputs)}

    '';

          else if valid == "warn" then

            (handleEvalWarning { inherit meta attrs; } { inherit (validity) reason errormsg; })

          else

            throw "Unknown validitiy: '${valid}'"

            throw "Unknown validity: '${valid}'"

        );

      };