fix warning obsolete code

Author: tranb3r

SecureHttpClient.Test/SpkiFingerprintTest.cs

@@ -19,7 +19,7 @@ public async Task SpkiFingerprintTest_RsaCertificate(string resource, string exp
 
             var certPem = await ResourceHelper.GetStringAsync(resource);
             var certBytes = System.Text.Encoding.ASCII.GetBytes(certPem);
-            var certificate = new X509Certificate2(certBytes);
+            var certificate = X509CertificateLoader.LoadCertificate(certBytes);
             var actual = SpkiFingerprint.Compute(certificate);
             Assert.Equal(expected, actual);
         }

SecureHttpClient/Platforms/Net/ClientCertificateProvider.cs

@@ -40,7 +40,7 @@ public class ImportedClientCertificateProvider : ClientCertificateProvider
         /// <param name="passphrase">The passphrase that protects the private key.</param>
         public void Import(byte[] certificate, string passphrase)
         {
-            Certificates.Add(new X509Certificate2(certificate, passphrase));
+            Certificates.Add(X509CertificateLoader.LoadPkcs12(certificate, passphrase));
         }
     }
 }

SecureHttpClient/Platforms/Net/SecureHttpClientHandler.cs

@@ -72,7 +72,7 @@ public virtual void SetTrustedRoots(params byte[][] certificates)
             _trustedRoots = new X509Certificate2Collection();
             foreach (var cert in certificates)
             {
-                _trustedRoots.Import(cert);
+                _trustedRoots.Add(X509CertificateLoader.LoadCertificate(cert));
             }
             ServerCertificateCustomValidationCallback = CheckServerCertificate;
         }

SecureHttpClient/Platforms/iOS/SecureHttpClientHandler.cs

@@ -68,7 +68,7 @@ public virtual void SetTrustedRoots(params byte[][] certificates)
             _trustedRoots = new X509Certificate2Collection();
             foreach (var cert in certificates)
             {
-                _trustedRoots.Import(cert);
+                _trustedRoots.Add(X509CertificateLoader.LoadCertificate(cert));
             }
         }