Don't export "hum" date versions for trade objects.

They are not used and have a rather high performance penalty due to
using arrow.get

tests/rpc/test_rpc_apiserver.py

@@ -755,7 +755,6 @@ def test_api_status(botclient, mocker, ticker, fee, markets):
         'amount_requested': 123.0,
         'base_currency': 'BTC',
         'close_date': None,
-        'close_date_hum': None,
         'close_timestamp': None,
         'close_profit': None,
         'close_profit_pct': None,
@@ -770,7 +769,6 @@ def test_api_status(botclient, mocker, ticker, fee, markets):
         'profit_fiat': ANY,
         'current_rate': 1.099e-05,
         'open_date': ANY,
-        'open_date_hum': ANY,
         'open_timestamp': ANY,
         'open_order': None,
         'open_rate': 0.123,
@@ -922,11 +920,9 @@ def test_api_forcebuy(botclient, mocker, fee):
         'amount_requested': 1,
         'trade_id': 22,
         'close_date': None,
-        'close_date_hum': None,
         'close_timestamp': None,
         'close_rate': 0.265441,
         'open_date': ANY,
-        'open_date_hum': 'just now',
         'open_timestamp': ANY,
         'open_rate': 0.245441,
         'pair': 'ETH/ETH',