Resolves 5542
Prior to rust-lang/rust#101212 the `ast::TraitObjectSyntax` enum only
had two variants `Dyn` and `None`. The PR that introduced the `dyn*`
syntax added a new variant `DynStar`, but did not update the formatting
rules to account for the new variant.
Now the new `DynStar` variant is properly handled and is no longer
removed by rustfmt.
