Remove deprecated plot_date calls

These were deprecated in Matplotlib 3.9.

Author: QuLogic

pandas/tests/plotting/test_datetimelike.py

@@ -1432,13 +1432,11 @@ def test_mpl_nopandas(self):
         values1 = np.arange(10.0, 11.0, 0.5)
         values2 = np.arange(11.0, 12.0, 0.5)
 
-        kw = {"fmt": "-", "lw": 4}
-
         _, ax = mpl.pyplot.subplots()
-        ax.plot_date([x.toordinal() for x in dates], values1, **kw)
-        ax.plot_date([x.toordinal() for x in dates], values2, **kw)
-
-        line1, line2 = ax.get_lines()
+        line1, line2, = ax.plot(
+            [x.toordinal() for x in dates], values1, "-",
+            [x.toordinal() for x in dates], values2, "-",
+            linewidth=4)
 
         exp = np.array([x.toordinal() for x in dates], dtype=np.float64)
         tm.assert_numpy_array_equal(line1.get_xydata()[:, 0], exp)