rustdoc: remove no-op CSS .content .item-info { position: relative }

This rule was added to help position the marker line in
110e727, which was a `position: absolute`
pseudo-element that relied on its parent to put it in the right spot.

The arrow was removed in 73d0f7c, so the
`relative` position is no longer necessary.

Author: notriddle

src/librustdoc/html/static/css/rustdoc.css

@@ -749,7 +749,6 @@ pre, .rustdoc.source .example-wrap {
 }
 
 .content .item-info {
-	position: relative;
 	margin-left: 24px;
 }