chore: satisfy unused_qualifications (again)

Regressed by
[#6354](https://github.com/gfx-rs/wgpu/pull/6354/files#diff-1dd0973ceb242a02442d33e422f9dff40e007b505d0ee726613e1763e61e768dR2809)
(CC @jimb). Hopefully will get plugged by
[#6105](#6105).

naga/src/back/spv/block.rs

@@ -2978,7 +2978,7 @@ impl<'w> BlockContext<'w> {
         let _ = self.write_block(
             entry_id,
             &self.ir_function.body,
-            super::block::BlockExit::Return,
+            BlockExit::Return,
             LoopContext::default(),
             debug_info,
         )?;