fix(examples): Remove stat_smooth to fix example tests

[karangattu]

I suspect that the issue happened because stat_smooth was trying to draw these trend lines, but some groups didn't have enough data points to create a meaningful line.
I’m not sure we really need to include stat_smooth in our example.

This is to fix the errors in the shiny console that caused the shiny examples tests to fail

/py-shiny/.venv/lib/python3.12/site-packages/plotnine/stats/stat_smooth.py:215: PlotnineWarning: Smoothing requires 2 or more points. Got 1. Not enough points for smoothing. If this message a surprise, make sure the column mapped to the x aesthetic has the right dtype.
/py-shiny/.venv/lib/python3.12/site-packages/statsmodels/regression/linear_model.py:1717: RuntimeWarning: divide by zero encountered in scalar divide
/py-shiny/.venv/lib/python3.12/site-packages/plotnine/stats/smoothers.py:562: RuntimeWarning: invalid value encountered in dot
/py-shiny/.venv/lib/python3.12/site-packages/plotnine/stats/stat_smooth.py:215: PlotnineWarning: Smoothing requires 2 or more points. Got 1. Not enough points for smoothing. If this message a surprise, make sure the column mapped to the x aesthetic has the right dtype.
/py-shiny/.venv/lib/python3.12/site-packages/statsmodels/regression/linear_model.py:1717: RuntimeWarning: divide by zero encountered in scalar divide
/py-shiny/.venv/lib/python3.12/site-packages/plotnine/stats/smoothers.py:562: RuntimeWarning: invalid value encountered in dot

[karangattu]

This might have fixed itself and maybe not required anymore. Hence closing