fix(axelar-gateway): ensure the testutils feature is loaded for tests (…

…#70)

contracts/axelar-gateway/src/auth.rs

@@ -236,7 +236,7 @@ fn validate_signers(env: &Env, weighted_signers: &WeightedSigners) -> Result<(),
     Ok(())
 }
 
-#[cfg(test)]
+#[cfg(all(test, feature = "testutils"))]
 mod tests {
     use crate::error::ContractError;
     use crate::testutils::TestSignerSet;