COMPAT: Fix the last warning from matplotlib 3.5.0 (pandas-dev#44544)

Author: lithomas1

pandas/plotting/_matplotlib/core.py

@@ -1036,7 +1036,6 @@ def _plot_colorbar(self, ax: Axes, **kwds):
         # use the last one which contains the latest information
         # about the ax
         img = ax.collections[-1]
-        ax.grid(False)
         cbar = self.fig.colorbar(img, ax=ax, **kwds)
 
         if mpl_ge_3_0_0():

pandas/tests/plotting/common.py

@@ -552,7 +552,7 @@ def is_grid_on():
             obj.plot(kind=kind, grid=False, **kws)
             assert not is_grid_on()
 
-            if kind != "pie":
+            if kind not in ["pie", "hexbin", "scatter"]:
                 self.plt.subplot(1, 4 * len(kinds), spndx)
                 spndx += 1
                 mpl.rc("axes", grid=True)