Update earth_relief test for SRTM15+ v2.4 release (GenericMappingTools#1863)

Author: Meghan Jones

pygmt/tests/test_datasets_earth_relief.py

@@ -42,7 +42,7 @@ def test_earth_relief_01d_with_region():
     assert data.shape == (11, 21)
     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(), -5147)
+    npt.assert_allclose(data.min(), -5154)
     npt.assert_allclose(data.max(), 805.5)