Update build_directory_md.py

[VaeterchenFrost]

Describe your change:

Propagate argument top_dir to good_file_paths.
Previously this argument did not get passed to the helper function when calling print_directory_md.
Introduced in a0817bd#diff-50223e3236c98dd66ef002e0c6dcde93

• Add an algorithm?
• [X ] Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• [ X] I have read CONTRIBUTING.md.
• [ X] This pull request is all my own work -- I have not plagiarized.
• [ X] I know that pull requests will not be merged if they fail the automated tests.
• [ X] This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• [ X] All new Python files are placed inside an existing directory.
• [X ] All filenames are in all lowercase characters with no spaces or dashes.
• [X ] All functions and variable names follow Python naming conventions.
• [X ] All function parameters and return values are annotated with Python type hints.
• [ X] All functions have doctests that pass the automated testing.
• [ X] All new algorithms have a URL in its comments that points to Wikipedia or other similar explanation.
• [ X] If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.