fix(nuget): allow duplicate packages in pacakge.config

[JamieMagee]

Without this we'll throw a PackagesConfigReaderException, and while duplicate packages in packages.config is not ideal, it is a supported scenario.

[github-actions]

👋 Hi! It looks like you modified some files in the Detectors folder.
You may need to bump the detector versions if any of the following scenarios apply:

• The detector detects more or fewer components than before
• The detector generates different parent/child graph relationships than before
• The detector generates different devDependencies values than before

If none of the above scenarios apply, feel free to ignore this comment 🙂