Fix display of warning block if it is first element of the top doc block

[GuillaumeGomez]

It fixes the display of the warning block "i" element in case it is the first element:

It now looks like this:

The update for the browser-ui-test framework is because it didn't detect correctly pseudo elements if they ended with a digit or a dash.

r? @notriddle

[rustbot]

Some changes occurred in HTML/CSS/JS.

cc @GuillaumeGomez, @jsha

[notriddle]

@bors r+ rollup

[bors]

📌 Commit 98b71bf has been approved by notriddle

It is now in the queue for this repository.

[bors]

⌛ Testing commit 98b71bf with merge b87f649...

[bors]

☀️ Test successful - checks-actions
Approved by: notriddle
Pushing b87f649 to master...

[rust-timer]

Finished benchmarking commit (b87f649): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	2
Improvements ✅ (secondary)	-0.4%	[-0.6%, -0.3%]	5
All ❌✅ (primary)	-0.7%	[-0.7%, -0.7%]	2

Max RSS (memory usage)

This benchmark run did not return any relevant results for this metric.

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 670.686s -> 672.006s (0.20%)
Artifact size: 312.64 MiB -> 312.63 MiB (-0.00%)