HADOOP-14655. Update httpcore version to 4.4.6. (rchiang)

hadoop-project/pom.xml

@@ -576,7 +576,7 @@
       <dependency>
         <groupId>org.apache.httpcomponents</groupId>
         <artifactId>httpcore</artifactId>
-        <version>4.4.4</version>
+        <version>4.4.6</version>
       </dependency>
       <dependency>
         <groupId>commons-codec</groupId>