fix: Update email wording for paid customers with API usage notifications

[zachaysan]

Changes

Update the API usage notification emails to remove mentions of grace period for paid accounts and to point people towards the ToS.

How did you test this code?

Ran the existing tests which all passed.

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

3 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
docs	⬜️ Ignored (Inspect)			Aug 19, 2024 3:38pm
flagsmith-frontend-preview	⬜️ Ignored (Inspect)			Aug 19, 2024 3:38pm
flagsmith-frontend-staging	⬜️ Ignored (Inspect)			Aug 19, 2024 3:38pm

[github-actions]

Docker builds report

Image	Build Status	Security report
ghcr.io/flagsmith/flagsmith-api-test:pr-4517	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-e2e:pr-4517	Finished ✅	Skipped
ghcr.io/flagsmith/flagsmith-frontend:pr-4517	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-api:pr-4517	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith-private-cloud:pr-4517	Finished ✅	Results ✅
ghcr.io/flagsmith/flagsmith:pr-4517	Finished ✅	Results ✅

[github-actions]

Uffizzi Preview deployment-55359 was deleted.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.92%. Comparing base (7034fa4) to head (0607240).
Report is 8 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4517   +/-   ##
=======================================
  Coverage   96.92%   96.92%           
=======================================
  Files        1178     1178           
  Lines       39489    39489           
=======================================
  Hits        38275    38275           
  Misses       1214     1214           

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