rustdoc: Remove unnecessary stability versions

For some reason only on enum and macro pages, the stability version is
rendered after the summary unlike all other pages. As it is already
displayed at the top of the page for all items, this removes it for
consistency and to prevent it from overlapping the summary text.

src/librustdoc/html/render.rs

@@ -2439,7 +2439,6 @@ fn item_enum(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
         write!(w, "}}")?;
     }
     write!(w, "</pre>")?;
-    render_stability_since_raw(w, it.stable_since(), None)?;
 
     document(w, cx, it)?;
     if !e.variants.is_empty() {
@@ -3055,7 +3054,6 @@ fn item_macro(w: &mut fmt::Formatter, cx: &Context, it: &clean::Item,
                                                      Some("macro"),
                                                      None,
                                                      None))?;
-    render_stability_since_raw(w, it.stable_since(), None)?;
     document(w, cx, it)
 }