HDFS-11438. Fix typo in error message of StoragePolicyAdmin tool. Contributed by Alison Yu.

hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/tools/StoragePolicyAdmin.java

@@ -259,7 +259,7 @@ public int run(Configuration conf, List<String> args) throws IOException {
       final String path = StringUtils.popOptionWithArgument("-path", args);
       if (path == null) {
         System.err.println("Please specify the path from which "
-            + "the storage policy will be unsetd.\nUsage: " + getLongUsage());
+            + "the storage policy will be unset.\nUsage: " + getLongUsage());
         return 1;
       }