hunspellDicts.nl_nl: move cc-by-nc-30 out of the license field since it is a unfree license

their readme says bsd3 and/or cc-by-nc-30

https://github.com/OpenTaal/opentaal-hunspell/blob/master/LICENSE.txt#L53

pkgs/development/libraries/hunspell/dictionaries.nix

···
     meta = with lib; {
       description = "Hunspell dictionary for Dutch (Netherlands) from OpenTaal";
       homepage = "https://www.opentaal.org/";
-      license = with licenses; [ bsd3 cc-by-nc-30 ];
+      license = with licenses; [ bsd3 ]; # and/or cc-by-nc-30
       maintainers = with maintainers; [ artturin ];
     };
   };