added ruff for code review

tests/test_optics.py

@@ -9,12 +9,12 @@ import pytest
 
 np = pytest.importorskip("numpy")
 
+from orisys_sensor_design.manifest import RevisionPaths, repo_root
 from orisys_sensor_design.optics import (
-    AIR_INDEX,
     Interface,
+    OpticalStack,
     OpticsConfigError,
     OpticsLayer,
-    OpticalStack,
     intersect_mesh,
     load_optics_block,
     quantify,
@@ -24,7 +24,6 @@ from orisys_sensor_design.optics import (
     trace_ray,
     validate_optics_block,
 )
-from orisys_sensor_design.manifest import RevisionPaths, repo_root
 
 REPO = repo_root()