Remove unused static references

Renci.SshClient/Renci.SshNet/Security/Cryptography/Ciphers/RsaCipher.cs

@@ -12,8 +12,6 @@ namespace Renci.SshNet.Security.Cryptography.Ciphers
     /// </summary>
     public class RsaCipher : AsymmetricCipher
     {
-        private static RNGCryptoServiceProvider _randomizer = new System.Security.Cryptography.RNGCryptoServiceProvider();
-
         private bool _isPrivate;
 
         private RsaKey _key;

Renci.SshClient/Renci.SshNet/Security/Cryptography/DsaDigitalSignature.cs

@@ -13,8 +13,6 @@ namespace Renci.SshNet.Security.Cryptography
     /// </summary>
     public class DsaDigitalSignature : DigitalSignature, IDisposable
     {
-        private static RNGCryptoServiceProvider _randomizer = new System.Security.Cryptography.RNGCryptoServiceProvider();
-        
         private HashAlgorithm _hash;
 
         private DsaKey _key;

Renci.SshClient/Renci.SshNet/Security/KeyExchangeDiffieHellman.cs

@@ -16,8 +16,6 @@ namespace Renci.SshNet.Security
     /// </summary>
     public abstract class KeyExchangeDiffieHellman : KeyExchange
     {
-        private static RNGCryptoServiceProvider _randomizer = new System.Security.Cryptography.RNGCryptoServiceProvider();
-
         /// <summary>
         /// Specifies key exchange group number.
         /// </summary>