[DE] all tens from 20 to 90 do not work

[mib1185]

In English this works perfect, but in German, the zero is always added to the tens (compared with English it would be "twenty-zero" instead of just "zwenty")

I've added some further tests to validate this and you see 21..29 are OK (20 is commented on purpose, to let the test fail at earliest on 30) but 30 results in "nullunddreißig" (thirty-zero) instead of "dreißig" (thirty)

    def test_german():
        engine = RbnfEngine.for_language("de")
        assert engine.format_number(1).text == "eins"
        assert engine.format_number(2).text == "zwei"
        assert engine.format_number(3).text == "drei"
        assert engine.format_number(4).text == "vier"
        assert engine.format_number(5).text == "fünf"
        assert engine.format_number(6).text == "sechs"
        assert engine.format_number(7).text == "sieben"
        assert engine.format_number(8).text == "acht"
        assert engine.format_number(9).text == "neun"
        assert engine.format_number(10).text == "zehn"
        assert engine.format_number(11).text == "elf"
        assert engine.format_number(12).text == "zwölf"
        assert engine.format_number(13).text == "dreizehn"
        assert engine.format_number(14).text == "vierzehn"
        assert engine.format_number(15).text == "fünfzehn"
        assert engine.format_number(16).text == "sechzehn"
        assert engine.format_number(17).text == "siebzehn"
        assert engine.format_number(18).text == "achtzehn"
        assert engine.format_number(19).text == "neunzehn"
        # assert engine.format_number(20).text == "zwanzig"
        assert engine.format_number(21).text == "einundzwanzig"
        assert engine.format_number(22).text == "zweiundzwanzig"
        assert engine.format_number(23).text == "dreiundzwanzig"
        assert engine.format_number(24).text == "vierundzwanzig"
        assert engine.format_number(25).text == "fünfundzwanzig"
        assert engine.format_number(26).text == "sechsundzwanzig"
        assert engine.format_number(27).text == "siebenundzwanzig"
        assert engine.format_number(28).text == "achtundzwanzig"
        assert engine.format_number(29).text == "neunundzwanzig"
>       assert engine.format_number(30).text == "dreißig"
E       AssertionError: assert 'nullunddreißig' == 'dreißig'
E         
E         
E         - dreißig
E         + nullunddreißig

[synesthesiam]

Fixed in 2.2.0