legend_tracegroupgap doesn't work when legend_traceorder is used

Note: to reproduce, see here

The problem

Baseline

long_df = px.data.medals_long()

fig = px.bar(long_df, x="nation", y="count", color="medal", title="Long-Form")
fig.update_layout(width=680, height=480,)
fig.show()

works just fine:

Increasing the gap works

long_df = px.data.medals_long()

fig = px.bar(long_df, x="nation", y="count", color="medal", title="Long-Form")
fig.update_layout(autosize=False, width=680, height=480, legend_tracegroupgap=50)
fig.show()

also works fine

Increasing the gap & reversing doesn't work

long_df = px.data.medals_long()

fig = px.bar(long_df, x="nation", y="count", color="medal", title="Long-Form Input")
fig.update_layout(width=680,height=480, legend_traceorder="reversed", legend_tracegroupgap=50)
fig.show()

gives

從連結的 Colab 重現開始，在 Plotly Python 入口中比較 legend_traceorder="reversed" 與 legend_tracegroupgap=50。追蹤這兩個版面配置屬性如何一同處理。完成標準是：反轉圖例 trace 順序後，設定的間距仍然可見。