## What changes were proposed in this pull request?
This is a very trivial PR, simply marking `strategies` in `SparkPlanner` with the `override` keyword for clarity since it is overriding `strategies` in `QueryPlanner` two levels up in the class hierarchy. I was reading through the code to learn a bit and got stuck on this fact for a little while, so I figured this may be helpful so that another developer new to the project doesn't get stuck where I was.
I did not make a JIRA ticket for this because it is so trivial, but I'm happy to do so to adhere to the contribution guidelines if required.
## How was this patch tested?
(Please explain how this patch was tested. E.g. unit tests, integration tests, manual tests)
(If this patch involves UI changes, please attach a screenshot; otherwise, remove this)
Please review http://spark.apache.org/contributing.html before opening a pull request.
Author: Eric Perry <eric@ericjperry.com>
Closes#19537 from ericjperry/override-strategies.
b84f61cd79