Fix GraphQL/FieldMethod offense (Part 2/2)

What does this MR do and why?

This fixes the GraphQL/FieldMethod offense in:

• ee/app/graphql/types/dast/profile_type.rb
• ee/app/graphql/types/dast_site_validation_type.rb
• ee/app/graphql/types/group_release_stats_type.rb
• ee/app/graphql/types/incident_management/oncall_rotation_type.rb

💁 This is the only MR in this series to modify files from ee/.

This MR is part 2 of a 2 part series of MRs to resolve #346031.

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