Correct purl error for namespaces

When there is namespace data for a package starting with "@", the purl has "%40" in place of the "@" in the in discoveredpackage worksheet (in Excel format) as in:

pkg:npm/%40babel/code-frame@7.5.5
pkg:npm/%40babel/core@7.7.7
pkg:npm/%40babel/generator@7.0.0-beta.44

The "@" shows correctly in the namespace column. I suspect that we should remove the "@" from the purl since we use "@" as the delimiter between name and version.