tox: Remove quotes around posargs

This was preventing us from doing e.g.:

  tox -e py36-django30 -- patchwork -v 2

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

tox.ini

@@ -25,7 +25,7 @@ passenv =
     PW_TEST_DB_TYPE PW_TEST_DB_USER PW_TEST_DB_PASS PW_TEST_DB_HOST
     PW_TEST_DB_PORT
 commands =
-    python {toxinidir}/manage.py test --noinput '{posargs:patchwork}'
+    python {toxinidir}/manage.py test --noinput {posargs:patchwork}
 
 [testenv:bashate]
 deps = bashate