Relax permissions for API prefix usage endpoint

[johannaengland]

Needed for subnet matrix tool to work for non-admin users. The frontend is using the prefix/usage/ API endpoint.

This bug was introduced in c2b9002.

Url: http://localhost/report/matrix/

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 0.00%. Comparing base (744afff) to head (a43c3c8).
Report is 2 commits behind head on 5.13.x.

Additional details and impacted files

@@      Coverage Diff       @@
##   5.13.x   #3374   +/-   ##
==============================
==============================

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.