Defaults control_finding_generator to null to allow Org to manage setting

[lorengordon]

No description provided.

[lorengordon]

Results of make test:

❯ make test PYTEST_ARGS="-v --nomock"
[bootstrap]: Using external tardigrade-ci, skipping auto-init
[pytest//home/loren/git/repos/tardigrade-ci/tests/terraform_pytest] Starting Python tests found under the directory "/home/loren/git/repos/tardigrade-ci/tests/terraform_pytest"
pytest /home/loren/git/repos/tardigrade-ci/tests/terraform_pytest -v --nomock
============================================================================= test session starts =============================================================================
platform linux -- Python 3.10.11, pytest-7.4.0, pluggy-1.2.0 -- /home/loren/.pyenv/versions/3.10.11/bin/python3.10
cachedir: .pytest_cache
rootdir: /home/loren/git/repos
collected 2 items

../tardigrade-ci/tests/terraform_pytest/test_terraform_install.py::test_modules[securityhub_cross_account] PASSED                                                                                                                                                                                                                             [ 50%]
../tardigrade-ci/tests/terraform_pytest/test_terraform_install.py::test_modules[securityhub_same_account] PASSED                                                                                                                                                                                                                              [100%]

======================================================================== 2 passed in 91.48s (0:01:31) =========================================================================
[pytest//home/loren/git/repos/tardigrade-ci/tests/terraform_pytest]: Tests executed!