Fix typo (#2246)

* Fix typo

---------

Signed-off-by: wangyitao <wangyitao999@outlook.com>

src/bthread/timer_thread.cpp

@@ -409,13 +409,13 @@ void TimerThread::run() {
         // Similarly with the situation before running tasks, we check
         // _nearest_run_time to prevent us from waiting on a non-earliest
         // task. We also use the _nsignal to make sure that if new task 
-        // is earlier that the realtime that we wait for, we'll wake up.
+        // is earlier than the realtime that we wait for, we'll wake up.
         int expected_nsignals = 0;
         {
             BAIDU_SCOPED_LOCK(_mutex);
             if (next_run_time > _nearest_run_time) {
-                // a task is earlier that what we would wait for.
-                // We need to check buckets.
+                // a task is earlier than what we would wait for.
+                // We need to check the buckets.
                 continue;
             } else {
                 _nearest_run_time = next_run_time;