Fix isort formatting

Technically this shouldn't be necessary, because isort aims to be
compatible with black which respects the trailing comma.

But the isort [fix][0] for this is not released yet.

[0]: PyCQA/isort#1876

Signed-off-by: Adam Cmiel <acmiel@redhat.com>

tests/unit/models/test_output.py

@@ -4,12 +4,7 @@
 import pydantic
 import pytest
 
-from cachi2.core.models.output import (
-    Dependency,
-    EnvironmentVariable,
-    Package,
-    RequestOutput,
-)
+from cachi2.core.models.output import Dependency, EnvironmentVariable, Package, RequestOutput
 
 
 class TestDependency: