deps: bump tar-fs to 2.1.5 in lambda zstd-layer example

[katsugtgz]

Updates tar-fs from 2.1.2 to 2.1.5 in examples/nodejs/aws/lambda-examples/advanced-compression-cdk/src/zstd-layer/nodejs/package-lock.json.

Evidence:

• the lockfile pinned tar-fs@2.1.2
• npm audit reported GHSA-8cj5-5rvv-wf4v and GHSA-vj76-c3g6-qr5v before the update
• updated version: 2.1.5

Validation:

• npm audit --omit=dev no longer reports either advisory after the update (0 vulnerabilities)
• npm ci --ignore-scripts resolves the edited lockfile cleanly

Scope: lockfile update only, in the lambda example above.