Resolve handler close race condition at triggerer shutdown

[dstandish]

At shutdown, a trigger may emit a "close" signal around the same time as logging.shutDown is called, so the handler may have been removed from the handlers by one thread when the other tries to delete it.

Example

[2024-02-06 11:39:26 +0000] [24] [INFO] Handling signal: term
[2024-02-06 11:39:26 +0000] [28] [INFO] Worker exiting (pid: 28)
[2024-02-06 11:39:26 +0000] [27] [INFO] Worker exiting (pid: 27)
[2024-02-06T11:38:08.264+0000] {triggerer_job_runner.py:623} INFO - trigger log_deferred_timestamp/manual__2024-02-06T11:33:03.922859+00:00/wait_for_time_348/-1/1 (ID 1051) completed
[2024-02-06 11:39:26 +0000] [24] [INFO] Shutting down: Master
Exception in thread Thread-1 (_monitor):
Traceback (most recent call last):
  File "/usr/local/lib/python3.11/threading.py", line 1045, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.11/threading.py", line 982, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/local/lib/python3.11/logging/handlers.py", line 1582, in _monitor
    self.handle(record)
  File "/usr/local/lib/python3.11/logging/handlers.py", line 1563, in handle
    handler.handle(record)
  File "/usr/local/lib/python3.11/site-packages/airflow/utils/log/trigger_handler.py", line 102, in handle
    self.close_one(record.trigger_id)
  File "/usr/local/lib/python3.11/site-packages/airflow/utils/log/trigger_handler.py", line 113, in close_one
    del self.handlers[trigger_id]
        ~~~~~~~~~~~~~^^^^^^^^^^^^
KeyError: 1052