Suppress unused_qualifications lint in generated code

```
error: unnecessary qualification
  --> tests/lint/../include/basic-safe-part.rs:76:12
   |
76 | impl<T, U> PinnedDrop for PinnedDropStruct<T, U> {
   |            ^^^^^^^^^^
   |
   = note: `-D unused-qualifications` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(unused_qualifications)]`
help: remove the unnecessary path segments
   |
76 | impl<T, U> PinnedDrop for PinnedDropStruct<T, U> {
   |
```

CHANGELOG.md

@@ -10,6 +10,8 @@ Note: In this file, do not use the hard wrap in the middle of a sentence for com
 
 ## [Unreleased]
 
+- Suppress `unused_qualifications` lint in generated code.
+
 ## [1.1.4] - 2024-01-25
 
 - Suppress `clippy::missing_docs_in_private_items` and `clippy::missing_inline_in_public_items` lints in generated code. ([#356](https://github.com/taiki-e/pin-project/pull/356), thanks @daxpedda)

pin-project-internal/src/pinned_drop.rs

@@ -47,6 +47,7 @@ pub(crate) fn attribute(args: &TokenStream, mut input: ItemImpl) -> TokenStream
         }
         tokens
     } else {
+        input.attrs.push(parse_quote!(#[allow(unused_qualifications)]));
         input.into_token_stream()
     }
 }

tests/expand/pinned_drop/enum.expanded.rs

@@ -149,6 +149,7 @@ const _: () = {
     }
 };
 #[doc(hidden)]
+#[allow(unused_qualifications)]
 impl<T, U> ::pin_project::__private::PinnedDrop for Enum<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]

tests/expand/pinned_drop/struct.expanded.rs

@@ -108,6 +108,7 @@ const _: () = {
     }
 };
 #[doc(hidden)]
+#[allow(unused_qualifications)]
 impl<T, U> ::pin_project::__private::PinnedDrop for Struct<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]

tests/expand/pinned_drop/tuple_struct.expanded.rs

@@ -102,6 +102,7 @@ const _: () = {
     }
 };
 #[doc(hidden)]
+#[allow(unused_qualifications)]
 impl<T, U> ::pin_project::__private::PinnedDrop for TupleStruct<T, U> {
     unsafe fn drop(self: Pin<&mut Self>) {
         #[allow(clippy::needless_pass_by_value)]

tests/include/basic.rs

@@ -2,17 +2,17 @@
 
 include!("basic-safe-part.rs");
 
-#[allow(clippy::undocumented_unsafe_blocks)]
+#[allow(unused_qualifications, clippy::undocumented_unsafe_blocks)]
 unsafe impl<T: ::pin_project::__private::Unpin, U: ::pin_project::__private::Unpin>
     ::pin_project::UnsafeUnpin for UnsafeUnpinStruct<T, U>
 {
 }
-#[allow(clippy::undocumented_unsafe_blocks)]
+#[allow(unused_qualifications, clippy::undocumented_unsafe_blocks)]
 unsafe impl<T: ::pin_project::__private::Unpin, U: ::pin_project::__private::Unpin>
     ::pin_project::UnsafeUnpin for UnsafeUnpinTupleStruct<T, U>
 {
 }
-#[allow(clippy::undocumented_unsafe_blocks)]
+#[allow(unused_qualifications, clippy::undocumented_unsafe_blocks)]
 unsafe impl<T: ::pin_project::__private::Unpin, U: ::pin_project::__private::Unpin>
     ::pin_project::UnsafeUnpin for UnsafeUnpinEnum<T, U>
 {