verusfmt errors on opens_invariants

[zeldovich]

The following piece of Verus code:

vstd::prelude::verus! {
    proof fn f() opens_invariants [ 123u8 ] {}
}

compiles with the latest version of verus just fine, but the latest verusfmt reports:

Error:   × Failed to parse
   ╭─[parse2.rs:1:1]
 1 │ vstd::prelude::verus! {
 2 │     proof fn f() opens_invariants [ 123u8 ] {}
   ·                                   ┬
   ·                                   ╰── here
 3 │ }
   ╰────
  help: Expected one of: COMMENT, opens_invariants_mode