Specify that CSOT prose test 11 only runs on standalone servers (#1672)

Author: baileympearson

source/client-side-operations-timeout/tests/README.md

@@ -606,6 +606,9 @@ Tests in this section MUST only run against replica sets and sharded clusters wi
 
 This test MUST only run against server versions 8.0+. This test must be skipped on Atlas Serverless.
 
+This test MUST only run against standalones. The bulkWrite call takes an exceedingly long time on replicasets and
+sharded clusters. Drivers MAY adjust the timeouts used in this test to allow for differing bulk encoding performance.
+
 1. Using `internalClient`, drop the `db.coll` collection.
 
 2. Using `internalClient`, set the following fail point: