support/testing/tests/package/test_shadow.py: drop blank line at end of file

Fixes:

support/testing/tests/package/test_shadow.py:55:1: W391 blank line at end of file
1     W391 blank line at end of file
make: *** [Makefile:1253: check-flake8] Error 123

https://gitlab.com/buildroot.org/buildroot/-/jobs/3918132888

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

support/testing/tests/package/test_shadow.py

@@ -52,4 +52,3 @@ class TestShadow(BRTest):
         self.assertRunOk(f'usermod {username} --home {new_home}')
         self.assertRunOk(f'test $(su {username} -c \'echo $HOME\') = {new_home}')
         self.assertRunOk(f'userdel {username}')
-