fix: incorrect pnames

[lars-reimann]

Closes #525.

Summary of Changes

Add missing slashes to the created pname properties.

Testing Instructions

1. Run

cd package-parser
poetry run parse-package api -p package_parser -s package_parser -o out

2. Check the pname properties.

[github-actions]

MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ CREDENTIALS	secretlint	yes		no	3.5s
✅ GIT	git_diff	yes		no	0.01s
✅ PYTHON	black	1	0	0	0.4s
✅ PYTHON	isort	1	0	0	0.17s
✅ PYTHON	mypy	1		0	5.34s

See errors details in artifact MegaLinter reports on CI Job page
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff