fix(access_token): use merchant_connector_id in access token (#5106)

crates/router/src/core/refunds.rs

@@ -447,7 +447,7 @@ pub async fn sync_refund_with_gateway(
  &state.conf.connectors,
  &connector_id,
  api::GetToken::Connector,
- payment_attempt.connector.clone(),
+ payment_attempt.merchant_connector_id.clone(),
  )
  .change_context(errors::ApiErrorResponse::InternalServerError)
  .attach_printable("Failed to get the connector")?;