Update "What's New in DevTools 128"

[leahmsft]

Rendered article for review:

• What's New in DevTools (Microsoft Edge 128)
  • https://review.learn.microsoft.com/en-us/microsoft-edge/devtools-guide-chromium/whats-new/2024/08/devtools-128?branch=pr-en-us-3256
    • Heap snapshot improvements
    • View WebSocket message activities in the Performance tool
  • Before/Live

This PR adds two new entries.

AB#53506860

[mikehoffms]

Approved the PR per Writer/Editor review, after making changes.

[learn-build-service-prod]

Learn Build status updates of commit b7ce13a:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-edge/devtools-guide-chromium/evaluate-performance/selector-stats.md	✅Succeeded	View
microsoft-edge/devtools-guide-chromium/experimental-features/index.md	✅Succeeded	View
microsoft-edge/devtools-guide-chromium/whats-new/2024/08/devtools-128-images/capture-settings-icon.png	✅Succeeded	View
microsoft-edge/devtools-guide-chromium/whats-new/2024/08/devtools-128-images/new-selector-stats.png	✅Succeeded	View
microsoft-edge/devtools-guide-chromium/whats-new/2024/08/devtools-128-images/old-selector-stats.png	✅Succeeded	View
microsoft-edge/devtools-guide-chromium/whats-new/2024/08/devtools-128.md	✅Succeeded	View
microsoft-edge/toc.yml	✅Succeeded	View

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