wxGUI/timeline: specify edgecolor to solve https://trac.osgeo.org/grass/ticket/3609

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@73019 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/timeline/frame.py

@@ -355,6 +355,7 @@ class TimelineFrame(wx.Frame):
                             i - 0.1,
                             0.2),
                         facecolors=color,
+                        edgecolor='black',
                         alpha=ALPHA))
             else:
                 plots.append(