Remove unnecessary unwrap_or

This was always questionable, and removing it doesn't fail any tests, so
I think this was not affecting the behavior. It dates all the way back
to the very first commit of rustdoc: 268f3f0

Author: jyn514

src/librustdoc/clean/mod.rs

@@ -254,7 +254,6 @@ impl Clean<Item> for doctree::Module<'_> {
             cx,
         );
         Item {
-            name: Some(what_rustc_thinks.name.unwrap_or_default()),
             attrs,
             source: span.clean(cx),
             ..what_rustc_thinks