Bar Legend Stroke Inconsistent after opacity change

[mrawdon]

Describe the bug
When changing the bar opacity. The legend text changes, it appears that the stroke property gets added to the text. This causes the text to appear bold.

To Reproduce

import numpy as np
from bqplot import (
    OrdinalScale,
    LinearScale,
    Bars,
    Figure,
    Axis
)

x_ord = OrdinalScale()
y_sc = LinearScale()

bar = Bars(x=np.arange(10),labels=["Bars"], y=np.random.rand(10), scales={"x": x_ord, "y": y_sc},display_legend=True)
ax_x = Axis(scale=x_ord)
ax_y = Axis(scale=y_sc, tick_format="0.2f", orientation="vertical")

def def_legend(src, event):
    bar.visible=not bar.visible
    if bar.visible:
        bar.opacities=[]
    else:
        bar.opacities=[.5]
    
bar.on_legend_click(def_legend) 

Figure(marks=[bar], axes=[ax_x, ax_y], padding_x=0.025, padding_y=0.025)

Click on the legend Text to reproduce

Expected behavior
I would expect the stroke property to remain the same in the legend after clicking Legend Text

Screenshots

After

After clicking again(should match first screenshot

Additional context
Looking at the code, it looks like in draw_legend the stroke property is never set.
In updateColors it appears that the stroke property always gets set.

I believe removing stroke from the legend in updateColors would address this issue. I can create a PR for that if that makes sense.