force_move: Use strings for axes to clear in clear_homing_state()

Pass a string such as "xyz" to kin.clear_homing_state().  This makes
the parameter a little less cryptic.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/kinematics/cartesian.py

@@ -72,10 +72,10 @@ class CartKinematics:
             else:
                 rail = self.rails[axis]
             self.limits[axis] = rail.get_range()
-    def clear_homing_state(self, axes):
-        for i, _ in enumerate(self.limits):
-            if i in axes:
-                self.limits[i] = (1.0, -1.0)
+    def clear_homing_state(self, clear_axes):
+        for axis, axis_name in enumerate("xyz"):
+            if axis_name in clear_axes:
+                self.limits[axis] = (1.0, -1.0)
     def home_axis(self, homing_state, axis, rail):
         # Determine movement
         position_min, position_max = rail.get_range()