Fix release compilation (#3417)

* Fix release

* typo

src/Neo/Ledger/MemoryPool.cs

@@ -660,9 +660,8 @@ internal bool ReVerifyTopUnverifiedTransactionsIfNeeded(int maxToVerify, DataCac
             return _unverifiedTransactions.Count > 0;
         }
 
-#if DEBUG
         // This method is only for test purpose
-        // Do not remove it from the DEBUG build
+        // Do not use this method outside of unit tests
         internal void Clear()
         {
             _txRwLock.EnterReadLock();
@@ -679,6 +678,5 @@ internal void Clear()
                 _txRwLock.ExitReadLock();
             }
         }
-#endif
     }
 }