tamer: bench: xir: Fix broken benchmark

This broke when I removed `SelfClose`.  I used to run
`make all fmt check bench` before every push, but they take a while to run,
in part because it uses nightly and has to recompile too.

But it looks like I need to be more diligent again.

tamer/benches/xir.rs

@@ -217,7 +217,7 @@ This is pretend fragment text.  We need a lot of it.</fragment>
                     Token::AttrValue(AttrValue::Escaped(val1), span),
                     Token::AttrName(attr2, span),
                     Token::AttrValue(AttrValue::Escaped(val2), span),
-                    Token::SelfClose(span),
+                    Token::Close(None, span),
                 ]
                 .into_iter()
                 .write(&mut buf, Default::default())