docs: Update architecture diagram image

[ps48]

Updated the architecture diagram image in the README to include RED metrics from Data prepper sent to Prometheus

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.62%. Comparing base (e4e2008) to head (b35c0a4).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #223   +/-   ##
=======================================
  Coverage   55.62%   55.62%           
=======================================
  Files           4        4           
  Lines         169      169           
  Branches       48       47    -1     
=======================================
  Hits           94       94           
  Misses         74       74           
  Partials        1        1           

☔ 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.

[kylehounslow]

Thanks @ps48, these look great!

Minor feedback: I initially misread the Data Prepper → Prometheus arrow as Data Prepper's own operational metrics until I noticed the "RED Metrics" label. Could we make the derivation more explicit? e.g. "RED Metrics (derived from traces)" on the arrow, so it's clear Data Prepper is computing these from spans rather than emitting them itself. Seems a bit verbose, but your call