DSLX formatting is weird for empty statement blocks

**Describe the bug**
The following is produced by our formatter:

```
proc A {
config() { }

init { }

next(_: ()) { }
}
```

**To Reproduce**
If the above is in a file pointed to by `$TESTFILE`, run `xls/dslx/dslx_fmt $TESTFILE`.

**Expected behavior**
Ideally, you'd get `config() {}` or even just one space.