Remove HasSpan trait.

The only place it is meaningfully used is in a panic message in
`TokenStream::from_ast`. But `node.span()` doesn't need to be printed
because `node` is also printed and it must contain the span.

compiler/rustc_resolve/src/late.rs

@@ -1744,7 +1744,7 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                             ) {
                                 self.r.dcx().emit_err(errors::LendingIteratorReportError {
                                     lifetime: lifetime.ident.span,
-                                    ty: ty.span(),
+                                    ty: ty.span,
                                 });
                             } else {
                                 self.r.dcx().emit_err(errors::AnonymousLivetimeNonGatReportError {