Use the same span for attributes and Try expansion of ?

This is needed for Clippy to know that the `#[allow(unused)]` attributes
added by the expansion of `?` are part of the desugaring, and that they
do not come from the user code.

rust-lang/rust-clippy#13380 exhibits a manifestation of this problem.

Author: samueltardieu

compiler/rustc_ast_lowering/src/expr.rs

@@ -1837,7 +1837,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             Safety::Default,
             sym::allow,
             sym::unreachable_code,
-            self.lower_span(span),
+            try_span,
         );
         let attrs: AttrVec = thin_vec![attr];