Update one existing test

Author: seisman

pygmt/tests/test_plot.py

@@ -483,14 +483,15 @@ def test_plot_timedelta64():
     """
     Test plotting numpy.timedelta64 input data.
     """
+    tmin, tmax = np.timedelta64(0, "D"), np.timedelta64(8, "D")
     fig = Figure()
     fig.basemap(
         projection="X8c/5c",
-        region=[0, 8, 0, 10],
+        region=[tmin, tmax, 0, 10],
         frame=["WSne", "xaf+lForecast Days", "yaf+lRMSE"],
     )
     fig.plot(
-        x=np.arange(np.timedelta64(0, "D"), np.timedelta64(8, "D")),
+        x=np.arange(tmin, tmax),
         y=np.geomspace(start=0.1, stop=9, num=8),
         style="c0.2c",
         pen="1p",