Revert "Make have_units_and_converter private"

This reverts commit a9cff25.

Author: ksunden

lib/matplotlib/axes/_base.py

@@ -2547,7 +2547,7 @@ def _process_unit_info(self, datasets=None, kwargs=None, *, convert=True):
             # Update from data if axis is already set but no unit is set yet.
             if (axis is not None and
                     data is not None and not
-                    axis._have_units_and_converter()):
+                    axis.have_units_and_converter()):
                 axis.update_units(data)
         for axis_name, axis in axis_map.items():
             # Return if no axis is set.

lib/matplotlib/axis.py

@@ -1733,7 +1733,7 @@ def have_units(self):
         """
         return self.converter is not None or self.units is not None
 
-    def _have_units_and_converter(self):
+    def have_units_and_converter(self):
         """
         Return `True` if units and a converter have been set.
         """