Incorrect PURL found while running export management command

`org.webjars.npm:jquery` should be a maven PURL, not a nuget PURL.

```python
Failed to process Package pkg:nuget/org.webjars.npm:jquery@3.5.0: ValueError('Invalid purl \'pkg:nuget/org.webjars.npm:jquery@3.5.0\' cannot contain a "user:pass@host:port" URL Authority component: \'\'.')
Traceback (most recent call last):
File "../vulnerablecode/vulnerabilities/management/commands/export.py", line 149, in export_data
ppath = hashid.get_package_purls_yml_file_path(purl)
File "../vulnerablecode/aboutcode/hashid/__init__.py", line 158, in get_package_purls_yml_file_path
return get_package_base_dir(purl) / PURLS_FILENAME
File "../vulnerablecode/aboutcode/hashid/__init__.py", line 147, in get_package_base_dir
purl = PackageURL.from_string(purl)
File "../vulnerablecode/venv/lib/python3.9/site-packages/packageurl/__init__.py", line 508, in from_string
raise ValueError(msg)
ValueError: Invalid purl 'pkg:nuget/org.webjars.npm:jquery@3.5.0' cannot contain a "user:pass@host:port" URL Authority component: ''.
```