[MINOR][SQL] Remove unused pattern matching variables in Optimizers.

## What changes were proposed in this pull request?

This PR removes unused pattern matching variable in Optimizers in order to improve readability.

## How was this patch tested?

Pass the existing Jenkins tests.

Author: Dongjoon Hyun <dongjoon@apache.org>

Closes #13145 from dongjoon-hyun/remove_unused_pattern_matching_variables.