Align coinbase download with ccxt limits

Align with https://github.com/ccxt/ccxt/issues/9268

freqtrade/exchange/coinbasepro.py

@@ -0,0 +1,23 @@
+""" CoinbasePro exchange subclass """
+import logging
+from typing import Dict
+
+from freqtrade.exchange import Exchange
+
+
+logger = logging.getLogger(__name__)
+
+
+class Coinbasepro(Exchange):
+    """
+    CoinbasePro exchange class. Contains adjustments needed for Freqtrade to work
+    with this exchange.
+
+    Please note that this exchange is not included in the list of exchanges
+    officially supported by the Freqtrade development team. So some features
+    may still not work as expected.
+    """
+
+    _ft_has: Dict = {
+        "ohlcv_candle_limit": 300,
+    }