rust/pv: Fix EC signature test

The size of an EC-secp521r1 signature can be up to 139 bytes (if ASN1
encoded). There is no lower bound, although sizes lower than 137 are
very unlikely but possible.

Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>

rust/pv/src/crypto.rs

@@ -350,7 +350,7 @@ mod tests {
 
         let data = "sample".as_bytes();
         let sign = sign_msg(&ec_key, MessageDigest::sha512(), data).unwrap();
-        assert!(sign.len() <= 139 && sign.len() >= 137);
+        assert!(sign.len() <= 139, "value is: {}", sign.len());
 
         assert!(verify_signature(&ec_key, MessageDigest::sha512(), data, &sign).unwrap());
     }