Line breaks are rendering as `<br>` inside of collapsible components

[shainaraskas]

Describe the bug

Line breaks written as + in the old system are being rendered with a plaintext <br> in the new system

raw asciidoc markup:

[[snowball_stemmers_have_been_upgraded]]
.Snowball stemmers have been upgraded
[%collapsible]
====
*Details* +
Lucene 10 ships with an upgrade of its Snowball stemmers.  For details see https://github.com/apache/lucene/issues/13209. Users using Snowball stemmers that are experiencing changes in search behaviour on  existing data are advised to reindex.

*Impact* +
The upgrade should generally provide improved stemming results. Small changes in token analysis can lead to mismatches with previously index data, so existing indices using Snowball stemmers as part of their analysis chain should be reindexed.
====

raw md markup:

::::{dropdown} Snowball stemmers have been upgraded
:name: snowball_stemmers_have_been_upgraded

**Details**<br> Lucene 10 ships with an upgrade of its Snowball stemmers.  For details see [https://github.com/apache/lucene/issues/13209](https://github.com/apache/lucene/issues/13209). Users using Snowball stemmers that are experiencing changes in search behaviour on  existing data are advised to reindex.

**Impact**<br> The upgrade should generally provide improved stemming results. Small changes in token analysis can lead to mismatches with previously index data, so existing indices using Snowball stemmers as part of their analysis chain should be reindexed.

::::

Expected behavior

<br> is replaced with a line break (either in the md file or the frontend)

example of how it looked in the old system:

Steps to reproduce

No response

Tooling

• docs-builder
• migration tooling
• I'm not sure

[georgewallace]

This is also showing outside of collapsible components. as you can find on https://bookish-dollop-9p66716.pages.github.io/common-log-format-example.html

[bmorelli25]

Fixed in #342.