docs(webpki-roots): simplify usage example

[robjtede]

copy-pasting the main usage example produces a clippy warning suggesting this instead

[cpu]

thanks for opening a PR 👍

[cpu]

CI failure is unrelated. Looks like there was an upstream data update between yesterday's cron run and this branch's run. We'll fix that separately.

[cpu]

CI failure is unrelated.

Ah, my mistake. It is related since the example is sourced from the template in the tooling it needs to be updated as well. @robjtede Can you update this place as well:

webpki-roots/webpki-roots/tests/codegen.rs

Lines 142 to 145 in 7edc915

	//! ```rust
	//! let root_store = rustls::RootCertStore {
	//! roots: webpki_roots::TLS_SERVER_ROOTS.iter().cloned().collect(),
	//! };

[ctz]

Thanks!