Rollup merge of #57954 - euclio:rustdoc-stability, r=QuietMisdreavus

rustdoc: remove blank unstable spans

Rustdoc generates blank unstable spans for unstable struct fields: ![screen shot 2019-01-28 at 1 05 04 pm](https://user-images.githubusercontent.com/1372438/51856295-5e8ed500-22fd-11e9-8074-025eddb4ef65.png)

This PR removes them:
![screen shot 2019-01-28 at 1 07 22 pm](https://user-images.githubusercontent.com/1372438/51856424-aada1500-22fd-11e9-86f0-34e2aa78b8b1.png)

r? @QuietMisdreavus

1 files changed, 0 insertions, 4 deletions

diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index 0b2e27eccff..c928edea75a 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -3484,10 +3484,6 @@ fn item_struct(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
                        ns_id = ns_id,
                        name = field.name.as_ref().unwrap(),
                        ty = ty)?;
-                if let Some(stability_class) = field.stability_class() {
-                    write!(w, "<span class='stab {stab}'></span>",
-                        stab = stability_class)?;
-                }
                 document(w, cx, field)?;
             }
         }