Update black, and run auto formatting over the codebase (#9381)

 - Update black version to the latest
 - Run black auto formatting over the codebase
    - Run autoformatting according to [`docs/code_style.md
`](https://github.com/matrix-org/synapse/blob/80d6dc9783aa80886a133756028984dbf8920168/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

1 files changed, 8 insertions, 4 deletions

diff --git a/tests/util/test_itertools.py b/tests/util/test_itertools.py
index 1ef0af8e8f..e931a7ec18 100644
--- a/tests/util/test_itertools.py
+++ b/tests/util/test_itertools.py
@@ -24,28 +24,32 @@ class ChunkSeqTests(TestCase):
         parts = chunk_seq("123", 8)
 
         self.assertEqual(
-            list(parts), ["123"],
+            list(parts),
+            ["123"],
         )
 
     def test_long_seq(self):
         parts = chunk_seq("abcdefghijklmnop", 8)
 
         self.assertEqual(
-            list(parts), ["abcdefgh", "ijklmnop"],
+            list(parts),
+            ["abcdefgh", "ijklmnop"],
         )
 
     def test_uneven_parts(self):
         parts = chunk_seq("abcdefghijklmnop", 5)
 
         self.assertEqual(
-            list(parts), ["abcde", "fghij", "klmno", "p"],
+            list(parts),
+            ["abcde", "fghij", "klmno", "p"],
         )
 
     def test_empty_input(self):
         parts = chunk_seq([], 5)
 
         self.assertEqual(
-            list(parts), [],
+            list(parts),
+            [],
         )