Update Polakdot mod Run-of-show UCB, clean & remove unused content

[nuke-web3]

Part of #791

https://github.com/Polkadot-Blockchain-Academy/pba-content/blob/main/syllabus/7-Polkadot/Readme.md has an incorrect version of what actually landed. So we have this correct for next time (at least the sequence and rough time spent on each part) we should update it.

We also have a few random odds and ends in the module dir that were not used. We should delete these and only keep the ones we did use. Prior versions can be found in tags for the final slides per cohort, and also the PR that removes them (if not existing in the BA slides for some reason)