Don't clip colorbar dividers

They are sometimes right on the edge of the Axes, and the last (or
possibly first) don't get drawn due to clipping. Because the divider
line width is the same as the Axes frame line width, we don't have to
worry about it going outside when unclipped.

Fixes matplotlib#22864

Author: QuLogic

lib/matplotlib/colorbar.py

@@ -434,7 +434,8 @@ def __init__(self, ax, mappable=None, *, cmap=None,
         self.dividers = collections.LineCollection(
             [],
             colors=[mpl.rcParams['axes.edgecolor']],
-            linewidths=[0.5 * mpl.rcParams['axes.linewidth']])
+            linewidths=[0.5 * mpl.rcParams['axes.linewidth']],
+            clip_on=False)
         self.ax.add_collection(self.dividers)
 
         self._locator = None