Remove unused HashUtils class

graphx/src/main/scala/org/apache/spark/graphx/util/HashUtils.scala

-package org.apache.spark.graphx.util
-
-
-object HashUtils {
-
-  /**
-   * Compute a 64-bit hash value for the given string.
-   * See http://stackoverflow.com/questions/1660501/what-is-a-good-64bit-hash-function-in-java-for-textual-strings
-   */
-  def hash(str: String): Long = {
-    var h = 1125899906842597L
-    val len = str.length
-    var i = 0
-
-    while (i < len) {
-      h = 31 * h + str(i)
-      i += 1
-    }
-    h
-  }
-}