This avoids event spans that would otherwise cause crashes, since an
End's span covers the range of the tag (which will be earlier than the
line break within the tag).
This is a follow-up for https://github.com/rust-lang/rust/pull/121659,
since most cases of unintended block quotes are lazy continuations.
The lint is designed to be more generally useful than that, though,
because it will also catch unintended list items and unintended
block quotes that didn't coincidentally hit a pulldown-cmark bug.