Remove volume mount from tests, this causes issues with gravity not being able to read an adlist file symlinked to /dev/null

Signed-off-by: Adam Warner <me@adamwarner.co.uk>

test/tests/conftest.py

@@ -35,19 +35,14 @@ def run_and_stream_command_output():
     return run_and_stream_command_output_inner
 
 
-@pytest.fixture()
-def args_volumes():
-    return "-v /dev/null:/etc/pihole/adlists.list"
-
-
 @pytest.fixture()
 def args_env():
     return '-e TZ="Europe/London"'
 
 
 @pytest.fixture()
-def args(args_volumes, args_env):
-    return "{} {}".format(args_volumes, args_env)
+def args(args_env):
+    return "{}".format(args_env)
 
 
 @pytest.fixture()