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
`](80d6dc9783/docs/code_style.md)
 - Update `code_style.md` docs around installing black to use the correct version

synapse/rest/client/v2_alpha/account.py

@@ -193,7 +193,10 @@ class PasswordRestServlet(RestServlet):
             requester = await self.auth.get_user_by_req(request)
             try:
                 params, session_id = await self.auth_handler.validate_user_via_ui_auth(
-                    requester, request, body, "modify your account password",
+                    requester,
+                    request,
+                    body,
+                    "modify your account password",
                 )
             except InteractiveAuthIncompleteError as e:
                 # The user needs to provide more steps to complete auth, but
@@ -312,7 +315,10 @@ class DeactivateAccountRestServlet(RestServlet):
             return 200, {}
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, request, body, "deactivate your account",
+            requester,
+            request,
+            body,
+            "deactivate your account",
         )
         result = await self._deactivate_account_handler.deactivate_account(
             requester.user.to_string(),
@@ -703,7 +709,10 @@ class ThreepidAddRestServlet(RestServlet):
         assert_valid_client_secret(client_secret)
 
         await self.auth_handler.validate_user_via_ui_auth(
-            requester, request, body, "add a third-party identifier to your account",
+            requester,
+            request,
+            body,
+            "add a third-party identifier to your account",
         )
 
         validation_session = await self.identity_handler.validate_threepid_session(