Bug summary

Hi,

When using triplot with a label the resulting legend contains two duplicated entries (even though the markers is None):

plt.triplot([0,2,1],[0,0,1],[[0,1,2]], label='Label'); 
plt.legend()

I think expected behavior would be either

1. Remove the second legend entry if no markers are given, or
2. Remove the second legend entry altogether, e.g. by using kw_markers.pop('label',None) around here

   matplotlib/lib/matplotlib/tri/triplot.py

   Line 78 in 2aa71eb

   }

Code for reproduction

see above

Actual outcome

see above

Expected outcome

see above

Additional information

No response

Operating system

MacOS

Matplotlib Version

3.6.0.dev2140+g2aa71eb355.d20220503

Matplotlib Backend

QtAgg

Python version

No response

Jupyter version

No response

Installation

pip