Fix the failing tests for the updated gebco dataset (#4055)

Author: seisman

pygmt/tests/test_datasets_earth_relief.py

@@ -49,7 +49,7 @@ def test_earth_relief_01d_gebco(data_source):
     assert data.gmt.registration is GridRegistration.GRIDLINE
     npt.assert_allclose(data.lat, np.arange(-90, 91, 1))
     npt.assert_allclose(data.lon, np.arange(-180, 181, 1))
-    npt.assert_allclose(data.min(), -7169.0, atol=1.0)
+    npt.assert_allclose(data.min(), -7173.0, atol=1.0)
     npt.assert_allclose(data.max(), 5350.0, atol=1.0)
 
 
@@ -83,7 +83,7 @@ def test_earth_relief_01d_with_region_gebco():
     assert data.gmt.registration is GridRegistration.GRIDLINE
     npt.assert_allclose(data.lat, np.arange(-5, 6, 1))
     npt.assert_allclose(data.lon, np.arange(-10, 11, 1))
-    npt.assert_allclose(data.min(), -5118.0, atol=1.0)
+    npt.assert_allclose(data.min(), -5137.0, atol=1.0)
     npt.assert_allclose(data.max(), 681.0, atol=1.0)