Revert "提供出现某种异常刷新代理，异常可配置"

This reverts commit 4a6441e.

Author: sutra

webmagic-core/src/main/java/us/codecraft/webmagic/downloader/HttpClientDownloader.java

@@ -4,7 +4,6 @@
 import java.nio.charset.Charset;
 import java.util.HashMap;
 import java.util.Map;
-import java.util.function.Predicate;
 
 import org.apache.commons.io.IOUtils;
 import org.apache.http.HttpResponse;
@@ -44,14 +43,6 @@ public class HttpClientDownloader extends AbstractDownloader {
 
     private boolean responseHeader = true;
 
-    private volatile boolean refreshProxyOnError = false;
-
-    private Predicate<Throwable> throwablePredicate = t->false;
-
-    public void setThrowablePredicate(Predicate<Throwable> predicate){
-        this.throwablePredicate = predicate;
-    }
-
     public void setHttpUriRequestConverter(HttpUriRequestConverter httpUriRequestConverter) {
         this.httpUriRequestConverter = httpUriRequestConverter;
     }