Fix style warning, “line longer than 100 chars”

Error was noted at 60643081 (L371)

I didn’t just put the content of the node on another line, because that would add spaces around the element content, messing up the JavaScript that checks what the content is.

src/librustdoc/html/render.rs

@@ -1460,7 +1460,8 @@ impl<'a> fmt::Display for Item<'a> {
         try!(write!(fmt, "<span class='out-of-band'>"));
         try!(write!(fmt,
         r##"<span id='render-detail'>
-            <a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">[&#x2212;]</a>
+            <a id="toggle-all-docs" href="javascript:void(0)"
+               title="collapse all docs">[&#x2212;]</a>
         </span>"##));
 
         // Write `src` tag