[TRIVIAL] Fix API error message (#3246)

# Description
The API expects camelCase query parameters and parses them into
snake_case Rust identifiers. Therefor the `API` actually expects the
query parameter `orderUid` and not `order_uid` which should be reflected
in the error message.

# Changes
Updated error message to be correct from the perspective of the API
consumer not the backend internals.

crates/orderbook/src/api/get_trades.rs

@@ -38,7 +38,7 @@ impl Query {
         match (self.order_uid.as_ref(), self.owner.as_ref()) {
             (Some(_), None) | (None, Some(_)) => Ok(self.trade_filter()),
             _ => Err(TradeFilterError::InvalidFilter(
-                "Must specify exactly one of owner and order_uid.".to_owned(),
+                "Must specify exactly one of owner or orderUid.".to_owned(),
             )),
         }
     }