Fix Vulnerabilities::Finding#remediations method

ee/app/models/vulnerabilities/finding.rb

@@ -241,7 +241,7 @@ module Vulnerabilities
     def remediations
       return metadata.dig('remediations') unless super.present?
 
-      super.as_json(only: [:summary, :diff])
+      super.as_json(only: [:summary], methods: [:diff])
     end
 
     def build_evidence_request(data)

ee/spec/models/vulnerabilities/finding_spec.rb

@@ -461,7 +461,7 @@ RSpec.describe Vulnerabilities::Finding do
 
     context 'when the finding has associated remediation records' do
       let!(:persisted_remediation) { create(:vulnerabilities_remediation, findings: [finding]) }
-      let(:remediation_hash) { persisted_remediation.as_json(only: [:summary, :diff]) }
+      let(:remediation_hash) { { 'summary' => persisted_remediation.summary, 'diff' => persisted_remediation.diff } }
 
       it { is_expected.to eq([remediation_hash]) }
     end