remove import

Author: arturobernalg

httpclient5/src/main/java/org/apache/hc/client5/http/impl/AlpnHeaderSupport.java

@@ -28,7 +28,6 @@
 
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
-import java.util.Collections;
 import java.util.List;
 
 import org.apache.hc.core5.annotation.Contract;