Revert "rustdoc search: prefer stable items in search results"

This reverts commit 1140e90074.

tests/rustdoc-js/sort-stability.js

@@ -1,9 +0,0 @@
-const EXPECTED = [
-    {
-        'query': 'foo',
-        'others': [
-            {"path": "sort_stability::old", "name": "foo"},
-            {"path": "sort_stability::new", "name": "foo"},
-        ],
-    },
-];

tests/rustdoc-js/sort-stability.rs

@@ -1,16 +0,0 @@
-#![feature(staged_api)]
-#![stable(feature = "foo_lib", since = "1.0.0")]
-
-#[stable(feature = "old_foo", since = "1.0.1")]
-pub mod old {
-    /// Old, stable foo
-    #[stable(feature = "old_foo", since = "1.0.1")]
-    pub fn foo() {}
-}
-
-#[unstable(feature = "new_foo", issue = "none")]
-pub mod new {
-    /// New, unstable foo
-    #[unstable(feature = "new_foo", issue = "none")]
-    pub fn foo() {}
-}