certificate serialNumber is not match

[Randyshu2018]

node version:10.15.3

steps to reproduce:

1. test certificate named cert.pem:

   -----BEGIN CERTIFICATE-----
   MIICKjCCAdGgAwIBAgIRAMGjl2AnD3bzdpQOcPOZ944wCgYIKoZIzj0EAwIwczEL
   MAkGA1UEBhMCVVMxEzARBgNVBAgTCkNhbGlmb3JuaWExFjAUBgNVBAcTDVNhbiBG
   cmFuY2lzY28xGTAXBgNVBAoTEG9yZzEuZXhhbXBsZS5jb20xHDAaBgNVBAMTE2Nh
   Lm9yZzEuZXhhbXBsZS5jb20wHhcNMjAwNjEyMDY0ODAwWhcNMzAwNjEwMDY0ODAw
   WjBsMQswCQYDVQQGEwJVUzETMBEGA1UECBMKQ2FsaWZvcm5pYTEWMBQGA1UEBxMN
   U2FuIEZyYW5jaXNjbzEPMA0GA1UECxMGY2xpZW50MR8wHQYDVQQDDBZVc2VyMUBv
   cmcxLmV4YW1wbGUuY29tMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAExkNePVH3
   8oQj1J2uBWU8e1E6GuvxKy3+yutI0+d2UVrMYkfu23Z+hvKiqmXI+DX1VUTmuaF9
   2du+kflKIS+Z0qNNMEswDgYDVR0PAQH/BAQDAgeAMAwGA1UdEwEB/wQCMAAwKwYD
   VR0jBCQwIoAgMofBUJnNe9UyITG0/au3jfNeJ4+g377clNphXQOvfIwwCgYIKoZI
   zj0EAwIDRwAwRAIgfzDtKejEx21PP/Vx2NPmaAVnAqPY30xMKAKCNVvYaSoCIAvT
   1rwBNvde855LUwMGtx3mBXx13gGrCl5dXxCXZHxG
   -----END CERTIFICATE-----

2. test.js

   
   const cp = require('child_process');
   const fs = require('fs');
   const { Certificate } = require('@fidm/x509');

const filePath = 'cert.pem';

const cert = Certificate.fromPEM(fs.readFileSync(filePath)); console.log(serial=${cert.serialNumber});

cp.spawn('openssl', [ 'x509', '-in', ${filePath}, '-serial', "-noout" ], { stdio: "inherit" });

3. run 
```bash
node test.js

4. output

   serial=00c1a39760270f76f376940e70f399f78e
   serial=C1A39760270F76F376940E70F399F78E