trivial: change word dispersion to distribution

Author: kay-kim

source/core/sharding-balancing.txt

@@ -45,7 +45,7 @@ To address uneven chunk distribution for a sharded collection, the
 balancer :doc:`migrates chunks </core/sharding-chunk-migration>` from
 shards with more chunks to shards with a fewer number of chunks. The
 balancer migrates the chunks, one at a time, until there is an even
-dispersion of chunks for the collection across the shards. For details
+distribution of chunks for the collection across the shards. For details
 about chunk migration, see :ref:`chunk-migration-procedure`.
 
 .. include:: /includes/fact-archiveMovedChunks.rst