rustdoc: `div.where` instead of fmt-newline class

This is about equally readable, a lot more terse, and stops
special-casing functions and methods.

```console
$ du -hs doc-old/ doc-new/
671M    doc-old/
670M    doc-new/
```

1 files changed, 2 insertions, 5 deletions

diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index d8250c273b0..b898eb5d381 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -703,11 +703,8 @@ pre, .rustdoc.src .example-wrap {
 	background: var(--table-alt-row-background-color);
 }
 
-/* Shift "where ..." part of method or fn definition down a line */
-.method .where,
-.fn .where,
-.where.fmt-newline {
-	display: block;
+/* "where ..." clauses with block display are also smaller */
+div.where {
 	white-space: pre-wrap;
 	font-size: 0.875rem;
 }