remove quantmaxpool

[capnramses]

Purpose of this PR

• Remove unused quantmaxpool functionality. Issue Remove QuantMaxPool #744.
• Familiarising myself with the dev & PR process by taking a small task.

Changes made in this PR

• Removed quant_max_pool functionality within files.
• Deleted 2x pool.py files that only used quant_max_pool functions.
• Removed import statements referring to the above files and functions.
• Removed inclusion of the above in handler lists.

Testing Summary

• Ran all the brevitas_examples tests before and after these edits.
• Ran a full local nox pass over the tests.
• Tested this Brevitas branch in a typical quantisation program of my own.

Risk Introduced / Breaking Changes

• I'm not 100% familiar with how this functionality was used, so I may have some testing gaps.

Pre-Merge Checklist

• Refresh branch from dev, resolve conflicts.
• Reviewed own PR and checked code.
• Initial PR CI/CD passing.
• Reviewed and approved.
• Full CI/CD passing.

[Giuseppe5]

We always merge PRs to dev and not master :)