chore: update margin/trading mode exception to be a configuration error

Author: xmatthias

freqtrade/exchange/exchange.py

@@ -877,8 +877,8 @@ def validate_trading_mode_and_margin_mode(
             (trading_mode, margin_mode) not in self._supported_trading_mode_margin_pairs
         ):
             mm_value = margin_mode and margin_mode.value
-            raise OperationalException(
-                f"Freqtrade does not support {mm_value} {trading_mode} on {self.name}"
+            raise ConfigurationError(
+                f"Freqtrade does not support '{mm_value}' '{trading_mode}' on {self.name}."
             )
 
     def get_option(self, param: str, default: Any | None = None) -> Any: