web: fix class feature type

[fariss]

capa JSON output with dnfile uses class_ instead of class for feature types. This PR fixes a bug that shows undefined for class feature types.

Example: rule encrypt data using AES via .NET in https://mandiant.github.io/capa/explorer/#/?rdoc=https://dpaste.org/wEWd9/raw

Checklist

• No CHANGELOG update needed

• No new tests needed

• No documentation update needed

[mr-tz]

can you explain the bug a bit more detailed please? is this an inconsistency in the result doc or just an assumption you made in the web ui?

[williballenthin]

oh sorry @mr-tz. let's continue the discussion here (despite the fact i merged) and can make follow up PRs if necessary.

[fariss]

Sorry for the lack of clarification here. Yes, this is an assumption I made thinking feature.class was used to denote the class used (e.g. System.Security.Cryptography.CryptoStream) but is actually feature.class_. There is no issues with the rdoc.

[mr-tz]

ok, great, thanks for the clarification