[Merged by Bors] - chore: remove some unused variables

[adomani]

Inspired by #17178 and found by a linter.

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[github-actions]

PR summary f70dfcdec4

Import changes for modified files

No significant changes to the import graph

Import changes for all files

Files	Import difference

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Declarations diff

No declarations were harmed in the making of this PR! 🐙

You can run this locally as follows

## summary with just the declaration names:
./scripts/declarations_diff.sh <optional_commit>

## more verbose report:
./scripts/declarations_diff.sh long <optional_commit>

The doc-module for script/declarations_diff.sh contains some details about this script.

[kim-em]

bors d+

[mathlib-bors]

✌️ adomani can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

[adomani]

!bench

[leanprover-bot]

Here are the benchmark results for commit f70dfcd.
There were no significant changes against commit 5a3902a.

[adomani]

bors merge

[mathlib-bors]

Pull request successfully merged into master.

Build succeeded:

• Build
• Lint style

[YaelDillies]

This strikes me as maybe not a useful change 😁

[adomani]

I see your point, but you can see that c and d alternate being implicit/explicit/non-present in the following lemmas and I do not think that d is ever used before c!