Follow-up from "Expose dismissal_reason on VulnerabilityType"

The following discussion from !124738 (merged) should be addressed:

• @thiagocsf started a discussion: (+1 comment)

  Question (non-blocking): wouldn't it also only return a value when state is dismissed?

  @Quintasan, for your consideration if it's worth updating the docs in a follow-up.

• @cablett started a discussion: (+1 comment)

  I wonder if all_graphql_fields_for might suit this better, but if there are fields you want to leave off, it might be fine.

Technical Writing suggestions:

• Separate these sentences. That's the format used in the example at https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#feature-flagged-field.
• Reverse the logic of the second sentence to make it easier to understand. As it is, it reads "Returns negative unless feature flag is positive". This phrasing is also in line with the text used in the example at https://docs.gitlab.com/ee/development/api_graphql_styleguide.html#feature-flagged-field.