Changing the backend in standalone script

#### ALL software version info
hvplot==0.10.0
polars==1.2.1
plotly==5.22.0
bokeh==3.4.2

#### Description of expected behavior and the observed behavior

I'm coming from this issue https://github.com/pola-rs/polars/issues/17647.
Changing the backend doesn't work, when using a `polars` dataframe with their `plot` namespace inside a standalone script or `marimo` notebooks. Somehow it works when using `jupyter=1.0.0`.

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

This script shows a bokeh plot, even though `plotly` was set as a backend:

```python
import polars as pl
import hvplot

hvplot.extension("plotly") # Setting the backend
plt = pl.DataFrame({"x": [1, 2, 3], "y": [3, 2, 1]}).plot.bar()
hvplot.show(plt)
```