docs: remove reference to SortEexc issue that is now resolved (#2464)

Author: andygrove

docs/source/user-guide/latest/tuning.md

@@ -27,9 +27,6 @@ Comet uses a global tokio runtime per executor process using tokio's defaults of
 maximum of 512 blocking threads. These values can be overridden using the environment variables `COMET_WORKER_THREADS`
 and `COMET_MAX_BLOCKING_THREADS`.
 
-DataFusion currently has a known issue when merging spill files in sort operators where the process can deadlock if
-there are more spill files than `COMET_MAX_BLOCKING_THREADS` ([tracking issue](https://github.com/apache/datafusion/issues/15323)).
-
 ## Memory Tuning
 
 It is necessary to specify how much memory Comet can use in addition to memory already allocated to Spark. In some