docs(external): fix memory enrichment table highlight wording

[pront]

Summary

Readers might find the sink terminology confusing.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

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References

[thomasqueirozb]

I feel like we should at least have the word sink somewhere. Source/Sink is a common pattern in CS in general

[datadog-vectordotdev]

Datadog Report

Branch report: pront/fix-wording-mem-highlight
Commit report: 656fd95
Test service: vector

✅ 0 Failed, 7 Passed, 0 Skipped, 25.26s Total Time