fix(sp41): trailing newline on carc_filter module + test (PEP 8)

backend/src/cyclone/rebill/carc_filter.py

@@ -41,4 +41,4 @@ def decide_carc(reasons: tuple[str, ...] | list[str]) -> CarcDecision:
         return CarcDecision.EXCLUDED
     if any(r in REVIEW_CARCS for r in reasons):
         return CarcDecision.REVIEW
-    return CarcDecision.REBILL
+    return CarcDecision.REBILL

backend/tests/test_rebill_carc_filter.py

@@ -46,4 +46,4 @@ def test_mixed_excluded_wins():
 def test_sets_have_expected_members():
     assert "CO-45" in EXCLUDED_CARCS
     assert "PI-16" in REVIEW_CARCS
-    assert "OA-18" in REVIEW_CARCS
+    assert "OA-18" in REVIEW_CARCS