[requires.io] dependency update

requires · requires · commit f1228fdf1ecd · 2021-06-21T19:57:30.000-07:00
diff --git a/tox.ini b/tox.ini
@@ -27,7 +27,7 @@ commands = pytest {posargs}
 [testenv:lint]
 deps =
     flake8>=3.8,<4
-    black==21.5b2
+    black==21.6b0
     mypy==0.902
     {[testenv]deps}
 commands =
