Bump pnpm/action-setup from 3 to 4

Bumps [pnpm/action-setup](https://github.com/pnpm/action-setup) from 3 to 4.
- [Release notes](https://github.com/pnpm/action-setup/releases)
- [Commits](pnpm/action-setup@v3...v4)

---
updated-dependencies:
- dependency-name: pnpm/action-setup
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/backend-tests.yml

@@ -29,7 +29,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 20
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         name: Install pnpm
         with:
           version: 8

.github/workflows/npmpublish.yml

@@ -27,7 +27,7 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: 20
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         name: Install pnpm
         with:
           version: 8
@@ -80,7 +80,7 @@ jobs:
         with:
           node-version: 20
           registry-url: https://registry.npmjs.org/
-      - uses: pnpm/action-setup@v3
+      - uses: pnpm/action-setup@v4
         name: Install pnpm
         with:
           version: 8