Rollup merge of #95587 - m-ou-se:std-remove-associated-type-bounds, r=Dylan-DPC

Remove need for associated_type_bounds in std.

library/std/src/lib.rs

@@ -224,7 +224,6 @@
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
-#![feature(associated_type_bounds)]
 #![feature(box_syntax)]
 #![feature(c_unwind)]
 #![feature(cfg_target_thread_local)]

library/std/src/sys/sgx/abi/usercalls/alloc.rs

@@ -571,7 +571,8 @@ impl<T: CoerceUnsized<U>, U> CoerceUnsized<UserRef<U>> for UserRef<T> {}
 impl<T, I> Index<I> for UserRef<[T]>
 where
     [T]: UserSafe,
-    I: SliceIndex<[T], Output: UserSafe>,
+    I: SliceIndex<[T]>,
+    I::Output: UserSafe,
 {
     type Output = UserRef<I::Output>;
 
@@ -591,7 +592,8 @@ where
 impl<T, I> IndexMut<I> for UserRef<[T]>
 where
     [T]: UserSafe,
-    I: SliceIndex<[T], Output: UserSafe>,
+    I: SliceIndex<[T]>,
+    I::Output: UserSafe,
 {
     #[inline]
     fn index_mut(&mut self, index: I) -> &mut UserRef<I::Output> {