Rollup merge of rust-lang#45245 - stjepang:more-padding-between-impls…

…, r=QuietMisdreavus

Rustdoc: Increase padding between consecutive impls

Currently, [implementors](https://doc.rust-lang.org/nightly/std/iter/trait.IntoIterator.html#implementors) list is a bit too condensed. More spacing makes the list easier to read.
Check out [this comment](rust-lang#41879 (comment)) to see what's the effect of this change.

Closes rust-lang#41879.

cc @QuietMisdreavus

src/librustdoc/html/static/rustdoc.css

@@ -394,7 +394,7 @@ h4 > code, h3 > code, .invisible > code {
 	padding: 0;
 }
 
-.content .item-list li { margin-bottom: 3px; }
+.content .item-list li { margin-bottom: 1em; }
 
 .content .multi-column {
 	-moz-column-count: 5;