### What needs to happen? In Spark Runner [`GroupNonMergingWindowsFunctions#groupByKeyInGlobalWindows`](https://github.com/apache/beam/blob/301286fd6a80bfae6f63d4998d002801716eceef/runners/spark/src/main/java/org/apache/beam/runners/spark/translation/GroupNonMergingWindowsFunctions.java#L266) does not use the partitioner passed as a parameter. ### Issue Priority Priority: 3 (nice-to-have improvement) ### Issue Components - [ ] Component: Python SDK - [X] Component: Java SDK - [ ] Component: Go SDK - [ ] Component: Typescript SDK - [ ] Component: IO connector - [ ] Component: Beam YAML - [ ] Component: Beam examples - [ ] Component: Beam playground - [ ] Component: Beam katas - [ ] Component: Website - [ ] Component: Infrastructure - [X] Component: Spark Runner - [ ] Component: Flink Runner - [ ] Component: Samza Runner - [ ] Component: Twister2 Runner - [ ] Component: Hazelcast Jet Runner - [ ] Component: Google Cloud Dataflow Runner