BUG: DatetimeIndex.delete with tz raises ValueError
Found and fixed `DatetimeIndex.delete` (#7302) results in `ValueError` when it has `tz` and `freq` is less than daily..

```
idx = pd.date_range(start='2011-01-01 09:00', periods=40, freq='H', tz='Asia/Tokyo')
idx.delete(0)
# ValueError: Inferred frequency None from passed dates does notconform to passed frequency H
```

`insert` (#7299) and `take` don't have problems, but changed test case to use hourly frequencies to detect this kind of problem.
