Fix grammar (#3635)

src/H5FDsubfiling/H5FDioc_threads.c

@@ -33,15 +33,15 @@ typedef struct ioc_data_t {
     hg_thread_pool_t *io_thread_pool;
     int64_t           sf_context_id;
 
-    /* sf_io_ops_pending is use to track the number of I/O operations pending so that we can wait
+    atomic_int sf_ioc_ready;
+    atomic_int sf_shutdown_flag;
+    /* sf_io_ops_pending tracks the number of I/O operations pending so that we can wait
      * until all I/O operations have been serviced before shutting down the worker thread pool.
      * The value of this variable must always be non-negative.
      *
      * Note that this is a convenience variable -- we could use io_queue.q_len instead.
      * However, accessing this field requires locking io_queue.q_mutex.
      */
-    atomic_int sf_ioc_ready;
-    atomic_int sf_shutdown_flag;
     atomic_int sf_io_ops_pending;
     atomic_int sf_work_pending;
 } ioc_data_t;