Label doesn't work with HLine

#### ALL software version info
Python 3.10.6
hvplot==0.8.3
holoviews==1.15.4
bokeh==2.4.3
jupyterlab==3.6.3

#### Description of expected behavior and the observed behavior
Should be able to add a label to HLine.

#### Complete, minimal, self-contained example code that reproduces the issue

```python
import pandas as pd
import hvplot.pandas
import holoviews as hv

df = pd.DataFrame([[1,2,3,4,5]])

df.hvplot.bar() * hv.HLine(df[0].mean(), label="Mean")

```