The `Format` implementations for various types were using a wildcard `_`
to match the `None` case on `Option<DisplayHint>`.
This is incorrect as it would also match any `Some(...)` variants that
were not explicitly handled, leading to unexpected behavior.
This commit changes the wildcard `_` to an explicit `None` match to
ensure that only the `None` case is handled, making the matching more
explicit and correct.
Signed-off-by: Xiaobo Liu <cppcoffee@gmail.com>