TST: Removing unnecessary cleanup decorator

[greglucas]

This removes the Matplotlib cleanup decorator as we are already handling the cleanup with the autouse fixture.

cartopy/lib/cartopy/tests/mpl/conftest.py

Lines 10 to 21 in 22cdafc

	@pytest.fixture(autouse=True)
	def mpl_test_cleanup(request):
	"""Runs tests in a context manager and closes figures after each test"""
	try:
	# Run each test in a context manager so that state does not leak out
	orig_backend = plt.get_backend()
	plt.switch_backend('Agg')
	with plt.rc_context():
	yield
	finally:
	# Closes all open figures and switches backend back to original
	plt.switch_backend(orig_backend)

closes #2020

[greglucas]

Test failures are all unrelated.