rustdoc: remove redundant item kind class from `.item-decl > pre`

This class originated in the very first commit of `rustdoc_ng`, and was used
to add a color border around the item decl based on its kind.

https://github.com/rust-lang/rust/blob/4fd061c426902b0904c65e64a3780b21f9ab3afb/src/rustdoc_ng/html/static/main.css#L102-L106

The item decl no longer has a border, and there aren't any
kind-specific styles in modern rustdoc's rendering of this UI item.

Most of this commit is updating test cases so that they use `item-decl` to
find the `<pre>` tag instead of relying on the fact that the class name
had `rust {kind}` in it while other `<pre>` tags only had class `rust`.

1 files changed, 2 insertions, 2 deletions

diff --git a/tests/rustdoc/toggle-item-contents.rs b/tests/rustdoc/toggle-item-contents.rs
index 87240f233ff..5d34ec09b66 100644
--- a/tests/rustdoc/toggle-item-contents.rs
+++ b/tests/rustdoc/toggle-item-contents.rs
@@ -81,8 +81,8 @@ pub enum EnumStructVariant {
 }
 
 // @has 'toggle_item_contents/enum.LargeEnum.html'
-// @count - '//*[@class="rust enum"]//details[@class="toggle type-contents-toggle"]' 1
-// @has - '//*[@class="rust enum"]//details[@class="toggle type-contents-toggle"]' 'Show 13 variants'
+// @count - '//div[@class="item-decl"]/pre//details[@class="toggle type-contents-toggle"]' 1
+// @has - '//div[@class="item-decl"]/pre//details[@class="toggle type-contents-toggle"]' 'Show 13 variants'
 pub enum LargeEnum {
     A, B, C, D, E, F(u8), G, H, I, J, K, L, M
 }