build(deps): bump actions/setup-node from 6 to 7

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 6 to 7.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](actions/setup-node@v6...v7)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '7'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/backend-tests.yml

@@ -42,7 +42,7 @@ jobs:
           repository: ether/etherpad-lite
           ref: ${{ matrix.core_ref }}
           path: etherpad-lite
-      - uses: actions/setup-node@v6
+      - uses: actions/setup-node@v7
         name: Install Node.js
         with:
           node-version: ${{ matrix.node }}

.github/workflows/frontend-tests.yml

@@ -33,7 +33,7 @@ jobs:
           repository: ether/etherpad-lite
           ref: ${{ matrix.core_ref }}
           path: etherpad-lite
-      - uses: actions/setup-node@v6
+      - uses: actions/setup-node@v7
         name: Install Node.js
         with:
           node-version: ${{ matrix.node }}

.github/workflows/npmpublish.yml

@@ -18,7 +18,7 @@ jobs:
       contents: write   # for the atomic version-bump push (branch + tag)
       id-token: write   # for npm OIDC trusted publishing
     steps:
-      - uses: actions/setup-node@v6
+      - uses: actions/setup-node@v7
         with:
           # OIDC trusted publishing needs npm >= 11.5.1, which requires
           # Node >= 20.17.0. setup-node's `20` resolves to the latest