Fixed compile error in db/column_family.cc

Summary:
Fixed the following compile error in db/column_family.cc
    db/column_family.cc:633:33: error: ‘ASSERT_GT’ was not declared in this scope
    16:14:45    ASSERT_GT(listeners.size(), 0U);

Test Plan: make db_test

Reviewers: igor, sdong, rven

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D38367

db/column_family.cc

@@ -630,7 +630,7 @@ void ColumnFamilyData::NotifyOnCompactionCompleted(
     DB* db, Compaction* c, const Status& status) {
 #ifndef ROCKSDB_LITE
   auto listeners = ioptions()->listeners;
-  ASSERT_GT(listeners.size(), 0U);
+  assert(listeners.size() > 0U);
   CompactionJobInfo info;
   info.cf_name = c->column_family_data()->GetName();
   info.status = status;