Remove pnpm/Javascript references

[cpengilly]

flagging that https://oplabs-pbc.slack.com/archives/CQZ0U9FAN/p1723164980130389|this results in the need for some doc updates. For example https://docs.optimism.io/chain/testing/dev-node#installation|here we still reference pnpm. The summary is that commands of the form pnpm foo:bar are now of the form just foo-bar, located in justfiles in the repo, though some may have changed names slightly