chore(deps): sync pnpm version into Dockerfiles

[gpazevedo]

Motivation and Context

=> ERROR [cdn builder 7/10] RUN pnpm install --filter=. 0.9s

[cdn builder 7/10] RUN pnpm install --filter=./cdn-server/cdn --filter=./cdn-server --frozen-lockfile:
0.821  ERR_PNPM_UNSUPPORTED_ENGINE  Unsupported environment (bad pnpm and/or Node.js version)
0.821
0.821 Your pnpm version is incompatible with "/app".
0.821
0.821 Expected version: 9
0.821 Got: 8.15.9

4 Dockerfiles have:
RUN npm install --global pnpm@8

Upgrading to:
RUN npm install --global pnpm@9

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[StarpTech]

LGTM, thanks for the fix!