eth: uncaptialize tracer preimage error message (#15792)

* eth: uncaptialize tracer preimage error message

* eth: improve very important error message

eth/api_tracer.go

@@ -674,7 +674,7 @@ func (api *PrivateDebugAPI) traceTx(ctx context.Context, message core.Message, v
 		return nil, fmt.Errorf("tracing failed: %v", err)
 	}
 	if err := core.WritePreimages(api.eth.ChainDb(), vmctx.BlockNumber.Uint64(), statedb.Preimages()); err != nil {
-		return nil, fmt.Errorf("Error writing preimage from trace: %v", err)
+		return nil, fmt.Errorf("can't write preimage: %v", err)
 	}
 	// Depending on the tracer type, format and return the output
 	switch tracer := tracer.(type) {