Fixed code snippet to actually create a large strings in the heap snapshot article

[captainbrosset]

Fixes #2851.

This should land at the same time as MicrosoftEdge/Demos#31 which changes the corresponding demo code.

Before: https://learn.microsoft.com/en-us/microsoft-edge/devtools-guide-chromium/memory-problems/heap-snapshots#naming-functions-to-differentiate-between-closures-in-the-snapshot
After: https://review.learn.microsoft.com/en-us/microsoft-edge/devtools-guide-chromium/memory-problems/heap-snapshots?branch=pr-en-us-2889#naming-functions-to-differentiate-between-closures-in-the-snapshot

AB#47200652

[learn-build-service-prod]

Learn Build status updates of commit 197064d:

✅ Validation status: passed

File	Status	Preview URL	Details
microsoft-edge/devtools-guide-chromium/memory-problems/heap-snapshots.md	✅Succeeded	View

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