Cleaned out unused imports

Author: Stephen Asbury

src/main/java/io/nats/client/impl/SSLUtils.java

@@ -14,10 +14,7 @@
 package io.nats.client.impl;
 
 import java.security.SecureRandom;
-import java.security.cert.Certificate;
-import java.security.cert.CertificateException;
 import java.security.cert.X509Certificate;
-import java.util.Set;
 
 import javax.net.ssl.SSLContext;
 import javax.net.ssl.TrustManager;