Mypy Denylist 'NOT_FULLY_COVERED_FILES' Referenced but Not Present

[Ash-2k3]

There seems to be an error in the Oppia Wiki regarding the Mypy checks configuration. According to the Backend Type Annotations Wiki Page, there should be a denylist called NOT_FULLY_COVERED_FILES inside scripts/run_mypy_checks.py. However, this denylist is not present in the codebase, which implies that all files are currently covered by Mypy checks.

Thus we would want to update the wiki to make sure wiki correctly reflects the current configuration of Mypy checks.