hir pretty: fix block indent
before:
```rust
fn main() {
{
{
::std::io::_print(format_arguments::new_const(&["Hello, world!\n"]));
};
}
}
```
after:
```rust
fn main() {
{
{
::std::io::_print(format_arguments::new_const(&["Hello, world!\n"]));
};
}
}
```
AST pretty does the same.