remove unused imports

Author: willschlitzer

pygmt/src/grdsample.py

@@ -4,7 +4,6 @@
 
 import xarray as xr
 from pygmt.clib import Session
-from pygmt.exceptions import GMTInvalidInput
 from pygmt.helpers import (
     GMTTempFile,
     build_arg_string,

pygmt/tests/test_grdsample.py

@@ -3,7 +3,6 @@
 """
 import os
 
-import numpy.testing as npt
 import pytest
 from pygmt import grdinfo, grdsample
 from pygmt.datasets import load_earth_relief