[MINOR][CORE][SQL] Remove explicit RDD and Partition overrides

## What changes were proposed in this pull request?

I **believe** that I _only_ removed duplicated code (that adds nothing but noise). I'm gonna remove the comment after Jenkins has built the changes with no issues and Spark devs has agreed to include the changes.

Remove explicit `RDD` and `Partition` overrides (that turn out code duplication)

## How was this patch tested?

Local build. Awaiting Jenkins.

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Author: Jacek Laskowski <jacek@japila.pl>

Closes #16145 from jaceklaskowski/rdd-overrides-removed.