Linear interpolation fails on tz-aware Series
The following code fails on 0.24.1, doesn't fail on 0.23.4 but result was wrong.

```python
from datetime import datetime, timezone, timedelta

start = datetime(2019, 1, 1, tzinfo=timezone.utc)

df = pd.DataFrame.from_records(
    {
        "date": [start + timedelta(days=i) for i in range(5)],
        "value": list(range(5)),
        "ref_date": [start + timedelta(days=i) for i in range(5)],
    }
)

df.set_index("date").resample("1H").interpolate("linear")
```

Things work again if:
- one makes `start` tz-naive;
- one removes column `ref_date`.