fix(lint): remove unused BottleImages imports from two test files

pyright strict reportUnusedImport flagged BottleImages in
test_docker_launch_committed_image.py and test_macos_container_launch.py;
neither file references the type by name (they only use the returned
value's attributes).

tests/unit/test_docker_launch_committed_image.py

@@ -13,7 +13,7 @@ from typing import Any
 from unittest import mock
 
 from bot_bottle.agent_provider import AgentProvisionPlan
-from bot_bottle.backend import BottleImages, BottleSpec
+from bot_bottle.backend import BottleSpec
 from bot_bottle.backend.docker import launch as launch_mod
 from bot_bottle.backend.docker.bottle_plan import DockerBottlePlan
 from bot_bottle.backend.docker.consolidated_launch import LaunchContext