[BUG] DataFrame.groupby.describe differs between cudf and pandas

**Describe the bug**
```
>>> import pandas as pd
>>> import cudf
>>> cudf.__version__
'22.12.00a+281.gcc4b4dd27c'
>>> data = {'a': ['b'], 'p': ['q'], 'n': [0]}
>>> pd.DataFrame(data).groupby('a').describe()
n
count mean std min 25% 50% 75% max
a
b 1.0 0.0 NaN 0.0 0.0 0.0 0.0 0.0
>>> cudf.DataFrame(data).groupby('a').describe()
p n
count min max count mean std min 25% 50% 75% max
a
b 1 q q 1 0.0 0 0.0 0.0 0.0 0
```

**Environment overview (please complete the following information)**
rapidsai/rapidsai-nightly:22.12-cuda11.5-runtime-rockylinux8-py3.9 on 29 nov 2022