`tt` is sometimes not translated

Mathlib (data/nat/basic):
```lean
@[simp] lemma bodd_bit1 (n) : bodd (bit1 n) = tt := bodd_bit tt n
```

Synport:
```lean
@[simp]
theorem bodd_bit1 (n) : bodd (bit1 n) = tt :=
  bodd_bit true n
```

This instance shows both `tt` being translated to `true`, as well as `tt` not being translated.