replaced _get_kw with kwargs.pop

_get_kw function is unnecessary because
kwargs.pop does exactly the same
5 jobs for plot_kwargs_pop in 2 minutes and 42 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build Docker
passed build_docker_from_cache #550760

00:00:14

 
  Test
passed test_python2_mpi #550763

00:02:06

passed test_python2_scalar #550761

00:02:06

65.0%
passed test_python3_mpi #550764

00:02:27

passed test_python3_scalar #550762

00:01:24