[Performance] Remove redundant JSON serialization in analytics

[gonzaloriestra]

Removed a redundant JSON.parse(JSON.stringify(payload)) cycle in packages/cli-kit/src/public/node/analytics.ts.

JSON.stringify automatically omits properties with undefined values, so the explicit cycle used to strip them was unnecessary as sanitizePayload performs its own JSON.stringify/JSON.parse cycle immediately after.

This change reduces CPU overhead and memory allocations during analytics reporting.

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PR created automatically by Jules for task 3531353586136633232 started by @gonzaloriestra

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