CI: Bump actions/setup-node from 5 to 6 (#1922)

Bumps [actions/setup-node](https://github.com/actions/setup-node) from 5 to 6.
- [Release notes](https://github.com/actions/setup-node/releases)
- [Commits](https://github.com/actions/setup-node/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/setup-node
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/benchmark.yml

@@ -19,7 +19,7 @@ jobs:
         with:
           ref: main
           path: main
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
         with:
           node-version: '>=20.6.0'
 

.github/workflows/docs.yml

@@ -14,6 +14,6 @@ jobs:
 
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-node@v5
+    - uses: actions/setup-node@v6
     - run: npm ci --ignore-scripts
     - run: npm run docs

.github/workflows/tests.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
       - name: Check for cached folders
         id: cache-full
         uses: actions/cache@v4
@@ -39,7 +39,7 @@ jobs:
     needs: build
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-node@v5
+    - uses: actions/setup-node@v6
       with:
         node-version: ${{ matrix.node-version }}
     - run: npm ci --ignore-scripts # for mocha
@@ -68,7 +68,7 @@ jobs:
 
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
 
       - name: Retrieve cached built folders
         uses: actions/cache/restore@v4
@@ -129,7 +129,7 @@ jobs:
     
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v5
+      - uses: actions/setup-node@v6
 
       - name: Generate self-signed HTTPS certificates for web-test-runner server
         uses: kofemann/action-create-certificate@v0.0.4
@@ -176,7 +176,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-node@v5
+    - uses: actions/setup-node@v6
     - run: npm ci --ignore-scripts # TS
     - name: Retrieve cached folders
       uses: actions/cache/restore@v4
@@ -195,7 +195,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v5
-    - uses: actions/setup-node@v5
+    - uses: actions/setup-node@v6
     - run: npm ci --ignore-scripts # linter
     - name: Retrieve cached folders
       uses: actions/cache/restore@v4