Remove Bittrex subclass

freqtrade/exchange/exchange.py

@@ -330,6 +330,7 @@ class Exchange:
         Exchange ohlcv candle limit
         Uses ohlcv_candle_limit_per_timeframe if the exchange has different limits
         per timeframe (e.g. bittrex), otherwise falls back to ohlcv_candle_limit
+        TODO: this is most likely no longer needed since only bittrex needed this.
         :param timeframe: Timeframe to check
         :param candle_type: Candle-type
         :param since_ms: Starting timestamp