Fix: rename certificate_total_produced_since_startup metric name in aggregator

[dlachaume]

Content

This PR includes the renaming of certificate_total_produced_since_startup metric (leftover related to the original name).

Pre-submit checklist

• Branch
  • Tests are provided (if possible)
  • Crates versions are updated (if relevant)
  • CHANGELOG file is updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • Update README file (if relevant)
  • Update documentation website (if relevant)
  • Add dev blog post (if relevant)

Issue(s)

Relates to #1980

[github-actions]

Test Results

    4 files  ±0     55 suites  ±0   10m 33s ⏱️ -1s
1 379 tests ±0  1 379 ✅ ±0  0 💤 ±0  0 ❌ ±0 
1 593 runs  ±0  1 593 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 0ed7499. ± Comparison against base commit f19e6a3.