Fix perf regression in rustdoc::bare_urls

[jyn514]

This regressed in #81764. After that PR, rustdoc compiled the regex for every single item in the crate: https://perf.rust-lang.org/compare.html?start=125505306744a0a5bb01d62337260a95d9ff8d57&end=2e495d2e845cf27740e3665f718acfd3aa17253e&stat=instructions%3Au

This would have been caught by clippy::declare_interior_mutable_const (cc #77983).

[rust-highfive]

r? @ollie27

(rust-highfive has picked a reviewer for you, use r? to override)

[jyn514]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 8c7b7dd with merge 47a47f0f8ba775de36a751857867bfbea8310770...

[Mark-Simulacrum]

r=me presuming perf looks good

[bors]

☀️ Try build successful - checks-actions
Build commit: 47a47f0f8ba775de36a751857867bfbea8310770 (47a47f0f8ba775de36a751857867bfbea8310770)

[rust-timer]

Queued 47a47f0f8ba775de36a751857867bfbea8310770 with parent bc66b92, future comparison URL.

[rust-timer]

Finished benchmarking try commit (47a47f0f8ba775de36a751857867bfbea8310770): comparison url.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying rollup- to bors.

Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf

[jyn514]

Yup, that was it.

@bors r=Mark-Simulacrum rollup=never

[bors]

📌 Commit 8c7b7dd has been approved by Mark-Simulacrum

[bors]

⌛ Testing commit 8c7b7dd with merge 8513e78...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 8513e78 to master...