maint: remove dead test cli flag (#21606)

## Summary & Motivation

https://dagsterlabs.slack.com/archives/C03AFEEDDNX/p1773246737232039

The flag is unused, adds complexity to the tests. Also added type annotations for pytest_addoption.

## Test Plan

CI

Internal-RevId: 70086e09a74b4fb3a52921d617168e2a8cdad671

Author: SpencerWhitehead7

conftest.py

@@ -13,7 +13,7 @@
     pass  # Not all test suites have dagster installed
 
 
-def pytest_addoption(parser):
+def pytest_addoption(parser: pytest.Parser):
     parser.addoption(
         "--split", action="store", default=None, help="Split test selection (e.g., 0/3)"
     )

examples/docs_snippets/docs_snippets_tests/conftest.py

@@ -36,7 +36,7 @@ def pytest_configure():
     os.environ[DG_UPDATE_CHECK_ENABLED_ENV_VAR] = "0"
 
 
-def pytest_addoption(parser: pytest.Parser) -> None:
+def pytest_addoption(parser: pytest.Parser):
     parser.addoption(
         "--update-snippets",
         action="store_true",

integration_tests/test_suites/celery-k8s-test-suite/conftest.py

@@ -37,7 +37,7 @@ def dagster_docker_image():
 
 
 # See: https://stackoverflow.com/a/31526934/324449
-def pytest_addoption(parser):
+def pytest_addoption(parser: pytest.Parser):
     # We catch the ValueError to support cases where we are loading multiple test suites, e.g., in
     # the VSCode test explorer. When pytest tries to add an option twice, we get, e.g.
     #

integration_tests/test_suites/k8s-test-suite/conftest.py

@@ -62,7 +62,7 @@ def dagster_docker_image() -> str:
 
 
 # See: https://stackoverflow.com/a/31526934/324449
-def pytest_addoption(parser) -> None:
+def pytest_addoption(parser: pytest.Parser):
     # We catch the ValueError to support cases where we are loading multiple test suites, e.g., in
     # the VSCode test explorer. When pytest tries to add an option twice, we get, e.g.
     #

python_modules/libraries/dagster-airflow/conftest.py

@@ -1,8 +1,10 @@
+import pytest
+
 pytest_plugins = ["dagster_test.fixtures"]
 
 
 # See: https://stackoverflow.com/a/31526934/324449
-def pytest_addoption(parser):
+def pytest_addoption(parser: pytest.Parser):
     # We catch the ValueError to support cases where we are loading multiple test suites, e.g., in
     # the VSCode test explorer. When pytest tries to add an option twice, we get, e.g.
     #

python_modules/libraries/dagster-celery/conftest.py

@@ -1,5 +1,8 @@
+import pytest
+
+
 # See: https://stackoverflow.com/a/31526934/324449
-def pytest_addoption(parser):
+def pytest_addoption(parser: pytest.Parser):
     # We catch the ValueError to support cases where we are loading multiple test suites, e.g., in
     # the VSCode test explorer. When pytest tries to add an option twice, we get, e.g.
     #