Option group_label does not work when plots are overlaid

[yt87]

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ALL software version info

hvplot                    0.10.0             pyhd8ed1ab_0    conda-forge
holoviews                 1.18.3             pyhd8ed1ab_0    conda-forge
bokeh                     3.4.1              pyhd8ed1ab_0    conda-forge

Description of expected behavior and the observed behavior

One can specify legend title with option group_label. However, the title disappears when 2 or more plots are overlaid. In the example below, p1 and p2 display the title, p1 * p2 does not.

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

# code goes here between backticks
df = pd.DataFrame([[0.2, 0.7], [0.8, 0.3]], index=[0, 1], columns=['a', 'b'])
p1 = df.hvplot.scatter(group_label='column')
p2 = df.hvplot.line(group_label='column')
p1 * p2

Stack traceback and/or browser JavaScript console output

Screenshots or screencasts of the bug in action

• [ ] I may be interested in making a pull request to address this