Address minor nits

Author: JoshRosen

core/src/main/scala/org/apache/spark/serializer/KryoSerializer.scala

@@ -127,7 +127,7 @@ class KryoSerializer(conf: SparkConf)
   }
 
   private[spark] override lazy val supportsRelocationOfSerializedObjects: Boolean = {
-    // If auto-flush is disabled, then Kryo may store references to duplicate occurrences of objects
+    // If auto-reset is disabled, then Kryo may store references to duplicate occurrences of objects
     // in the stream rather than writing those objects' serialized bytes, breaking relocation. See
     // https://groups.google.com/d/msg/kryo-users/6ZUSyfjjtdo/FhGG1KHDXPgJ for more details.
     newInstance().asInstanceOf[KryoSerializerInstance].getAutoReset()

core/src/main/scala/org/apache/spark/serializer/Serializer.scala

@@ -23,7 +23,7 @@ import java.nio.ByteBuffer
 import scala.reflect.ClassTag
 
 import org.apache.spark.{SparkConf, SparkEnv}
-import org.apache.spark.annotation.{Private, Experimental, DeveloperApi}
+import org.apache.spark.annotation.{DeveloperApi, Private}
 import org.apache.spark.util.{Utils, ByteBufferInputStream, NextIterator}
 
 /**