Remove unused Hash impl from DocFragmentKind

Author: notriddle

src/librustdoc/clean/types.rs

@@ -994,7 +994,7 @@ pub(crate) struct DocFragment {
 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
 rustc_data_structures::static_assert_size!(DocFragment, 32);
 
-#[derive(Clone, Copy, PartialEq, Eq, Debug, Hash)]
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
 pub(crate) enum DocFragmentKind {
     /// A doc fragment created from a `///` or `//!` doc comment.
     SugaredDoc,