Consider removing PYSEC importer and keep PYPA importer only

[TG1999]

• https://github.com/aboutcode-org/vulnerablecode/blob/main/vulnerabilities/pipelines/v2_importers/pypa_importer.py
• https://github.com/aboutcode-org/vulnerablecode/blob/main/vulnerabilities/pipelines/v2_importers/pysec_importer.py

Currently we have both importers and they are potentially importing same data, we need to verify and remove pysec_importer since pypa_importer provides more better and closer source like this:

• https://github.com/pypa/advisory-database/blob/main/vulns/aamiles/PYSEC-2022-43066.yaml

Whereas pysec provides a zip URL only

https://osv-vulnerabilities.storage.googleapis.com/PyPI/all.zip