[NO ISSUE][OTR] Remove Unused Storage Constants

- user model changes: no
- storage format changes: no
- interface changes: no

Details:
- Remove unused storage constants that were used
  for storage backward compatibility.

Change-Id: I68baa806409ca8714d1a35a6cbe290d5ab150778
Reviewed-on: https://asterix-gerrit.ics.uci.edu/2600
Sonar-Qube: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Tested-by: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Murtadha Hubail <mhubail@apache.org>
Contrib: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Integration-Tests: Jenkins <jenkins@fulliautomatix.ics.uci.edu>
Reviewed-by: Michael Blow <mblow@apache.org>
diff --git a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/utils/StorageConstants.java b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/utils/StorageConstants.java
index 265c9fd..f6aa2c3 100644
--- a/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/utils/StorageConstants.java
+++ b/asterixdb/asterix-common/src/main/java/org/apache/asterix/common/utils/StorageConstants.java
@@ -37,7 +37,6 @@
     public static final String METADATA_FILE_NAME = ".metadata";
     public static final String MASK_FILE_PREFIX = ".mask_";
     public static final String COMPONENT_MASK_FILE_PREFIX = MASK_FILE_PREFIX + "C_";
-    public static final String LEGACY_DATASET_INDEX_NAME_SEPARATOR = "_idx_";
 
     /**
      * The storage version of AsterixDB related artifacts (e.g. log files, checkpoint files, etc..).
@@ -49,11 +48,6 @@
      */
     public static final int VERSION = LOCAL_STORAGE_VERSION + ITreeIndexFrame.Constants.VERSION;
 
-    /**
-     * The storage version in which the rebalance storage structure was introduced
-     */
-    public static final int REBALANCE_STORAGE_VERSION = 8;
-
     private StorageConstants() {
     }
 }
\ No newline at end of file