Switch to `pnpm pack --json`

[karlhorky]

Partial revert of #597

Originally, implemented a workaround to resolve the failure with pnpm@9.13.0:

• feat: display packed files list in pnpm pack pnpm/pnpm#8707 (comment)

pnpm accepted a PR to enable pnpm pack --json, which will probably be released in pnpm@8.13.3 or pnpm@8.14.0:

• pnpm pack JSON output option pnpm/pnpm#8764 (comment)