Update primer.json to reflect Black's adoption (psf#1674)

- tox recently adopted Black  
tox-dev/tox@a790350

- attrs already adopted Black but they updated to 20.08b1 + did a format pass and removed some trailing commas
python-attrs/attrs@f680c5b

src/black_primer/primer.json

@@ -10,7 +10,7 @@
     },
     "attrs": {
       "cli_arguments": [],
-      "expect_formatting_changes": true,
+      "expect_formatting_changes": false,
       "git_clone_url": "https://github.com/python-attrs/attrs.git",
       "long_checkout": false,
       "py_versions": ["all"]
@@ -98,7 +98,7 @@
     },
     "tox": {
       "cli_arguments": [],
-      "expect_formatting_changes": true,
+      "expect_formatting_changes": false,
       "git_clone_url": "https://github.com/tox-dev/tox.git",
       "long_checkout": false,
       "py_versions": ["all"]