doc: add PerformanceObserverEntryList export history

[henriquejsza]

Summary

• Add the missing v16.7.0 history entry for PerformanceObserverEntryList being exported from node:perf_hooks.
• Clarify that the constructor is not exposed directly, matching nearby perf_hooks class wording.

Details

PerformanceObserverEntryList instances existed before v16.7.0, but the class was not exported from node:perf_hooks until #39532, which was included in v16.7.0.

Fixes: #55815
Refs: #39532

Validation

• make lint-md
• node tools/lint-md/lint-md.mjs doc/api/perf_hooks.md
• make doc-only
• git diff --check

[github-actions]

This pull request has been marked as stale due to 90 days of inactivity.
It will be automatically closed in 30 days if no further activity occurs. If this is still relevant, please leave a comment or update it to keep it open.

[henriquejsza]

Still relevant: current main still lacks the v16.7.0 export history for PerformanceObserverEntryList, and this PR is currently mergeable. Keeping it open.