DOCSP-27813 chunk migration concurrency limitation (#2509)

* DOCSP-27813-chunkMigrationConcurrency-limitation

* DOCSP-27813-chunkMigrationConcurrency-limitation

* DOCSP-27813-chunkMigrationConcurrency-limitation

* DOCSP-27813-chunkMigrationConcurrency-limitation

---------

Co-authored-by: jason-price-mongodb <[email protected]>

Author: jason-price-mongodb

source/reference/parameters.txt

@@ -3032,6 +3032,12 @@ Sharding Parameters
    Maximum value is 500. You should typically use fewer than 32 threads
    unless you are using NVMe (Non-Volatile Memory Express) disks.
 
+   If ``chunkMigrationConcurrency`` is greater than ``1``, the
+   ``_secondaryThrottle`` configuration setting is ignored. The
+   ``_secondaryThrottle`` setting determines when the chunk migration
+   proceeds with the next document in the chunk. For details, see
+   :ref:`chunk-migration-replication`.
+
    The following example sets ``chunkMigrationConcurrency`` to ``5``:
 
    .. code-block:: bash