docs: Use easier to understand `no_run` attribute

This makes all bash code blocks use the bash language indicator but the fragments which should not be tangled out are marked with a more Rust-familiar no_run attribute instead of sh.

All markdown forges I tested rendered this just fine.

Context: I spent a couple of minutes figuring out why my addition to README is not getting run and the bash/sh split was slightly too easy to oversight 😅