PHPLIB-364: Document that transactions do not allow per-op read/write concerns

docs/includes/apiargs-MongoDBCollection-common-option.yaml

@@ -42,6 +42,11 @@ description: |
 
    This is not supported for server versions prior to 3.2 and will result in an
    exception at execution time if used.
+
+   It is not possible to specify a :manual:`read concern
+   </reference/read-concern>` for individual operations as part of a
+   transaction. Instead, set the ``readConcern`` option when starting the
+   transaction with :php:`startTransaction <mongodb-driver-session.starttransaction>`.
 interface: phpmethod
 operation: ~
 optional: true
@@ -68,6 +73,11 @@ type: :php:`MongoDB\\Driver\\WriteConcern <class.mongodb-driver-writeconcern>`
 description: |
    :manual:`Write concern </reference/write-concern>` to use for the operation.
    Defaults to the collection's write concern.
+
+   It is not possible to specify a :manual:`write concern
+   </reference/write-concern>` for individual operations as part of a
+   transaction. Instead, set the ``writeConcern`` option when starting the
+   transaction with :php:`startTransaction <mongodb-driver-session.starttransaction>`.
 interface: phpmethod
 operation: ~
 optional: true