chore(deps): drop pnpm-lock.yaml from the PR diff

doc/DEVELOPING.md forbids a pnpm-lock.yaml change in a pull request.
GitHub Actions owns the lockfile: its policy job regenerates it on
the fly and shares the regenerated file with downstream jobs, so the
committed manifest change in server/package.json is enough on its
own.

Restore pnpm-lock.yaml to the copy on master. Keep the postgres
devDependency entry in server/package.json for the null-socket guard
test.

Co-authored-by: Paperclip <noreply@paperclip.ing>

pnpm-lock.yaml

@@ -990,9 +990,6 @@ importers:
       cross-env:
         specifier: ^10.1.0
         version: 10.1.0
-      postgres:
-        specifier: ^3.4.9
-        version: 3.4.9
       supertest:
         specifier: ^7.0.0
         version: 7.2.2