minor #13775 [Lock] #37139 Updated Lock MongoDbStore note on readPreference (kralos)

This PR was merged into the 5.1 branch.

Discussion
----------

[Lock] #37139 Updated Lock MongoDbStore note on readPreference

Fixed documentation around `readPreference` for `MongoDbStore` in `Lock` component. See symfony/symfony#37140

Commits
-------

98574f5 #37139 Updated Lock MongoDbStore note on readPreference

Author: javiereguiluz

components/lock.rst

@@ -682,9 +682,10 @@ about `Expire Data from Collections by Setting TTL`_ in MongoDB.
     locks don't expire prematurely; the lock TTL should be set with enough extra
     time in ``expireAfterSeconds`` to account for any clock drift between nodes.
 
-``writeConcern``, ``readConcern`` and ``readPreference`` are not specified by
-MongoDbStore meaning the collection's settings will take effect. Read more
-about `Replica Set Read and Write Semantics`_ in MongoDB.
+``writeConcern`` and ``readConcern`` are not specified by MongoDbStore meaning
+the collection's settings will take effect.
+``readPreference`` is ``primary`` for all queries.
+Read more about `Replica Set Read and Write Semantics`_ in MongoDB.
 
 PdoStore
 ~~~~~~~~~~