manager: fix bug in ignore pattern for black in pyproject.toml

manager/pyproject.toml

@@ -81,8 +81,10 @@ line-length = 120
 target_version = ['py38']
 include = '\.py$'
 exclude = '''
-^/setup.py  # Poetry generates it and we want to keep it unchanged
-knot_resolver_manager/__main__.py  # due to pretty syntax error blocking old versions of python
+^/(
+    setup.py    # Poetry generates it and we want to keep it unchanged
+    | knot_resolver_manager/__main__.py    # due to pretty syntax error blocking old versions of python
+)
 '''
 
 [tool.isort]