Investigate inconsistencies between running `’dot shorthands: single-stepping’` test with `ModuleFormat.ddc` v.s. with `ModuleFormat.amd`

`dwds/test/instances/common/dot_shorthands_common.dart` currently contains the following lines:

```
if (provider.ddcModuleFormat == ModuleFormat.ddc)
  '$scriptBasename:$lineB:20', // on '2'
```

An investigation should be performed to figure out why the `if` guard is needed.