refact code

Author: platinumhamburg

fluss-server/src/main/java/org/apache/fluss/server/kv/KvManager.java

@@ -314,8 +314,6 @@ public void dropKv(TableBucket tableBucket) {
             try {
                 // Unregister RocksDB metrics from TableMetricGroup
                 serverMetricGroup.unregisterRocksDBMetrics(tablePath, tableBucket);
-                // Remove bucket metric group and clean up table metric group if needed
-                serverMetricGroup.removeTableBucketMetricGroup(tablePath, tableBucket);
 
                 dropKvTablet.drop();
                 if (dropKvTablet.getPartitionName() == null) {

fluss-server/src/main/java/org/apache/fluss/server/kv/rocksdb/RocksDBMetrics.java

@@ -224,7 +224,7 @@ public long getTotalMemoryUsage() {
                 return 0L;
             }
 
-            // Create cache set for memory usage calculation
+            // Create cache set for memory usage calculation.
             // If blockCache is null, pass null to MemoryUtil (will only count memtables, etc.)
             Set<Cache> caches = null;
             if (blockCache != null) {