Show hidden items with rustdoc's document-private

When using `#[doc(hidden)]` elements are hidden from docs even when the
rustdoc flag `--document-private-items` is set.

This behavior has been changed to display all hidden items when the flag
is active.

src/librustdoc/lib.rs

@@ -470,7 +470,6 @@ where R: 'static + Send, F: 'static + Send + FnOnce(Output) -> R {
         default_passes = false;
 
         passes = vec![
-            String::from("strip-hidden"),
             String::from("collapse-docs"),
             String::from("unindent-comments"),
         ];

src/test/rustdoc/issue-46380.rs

@@ -0,0 +1,15 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// compile-flags: --document-private-items
+
+// @has issue_46380/struct.Hidden.html
+#[doc(hidden)]
+pub struct Hidden;