chore: update setup-node in github workflows (#2161)

Source-Link: googleapis/synthtool@bfba274
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:da8a4a745d5eb96f07fa99a550afe49ac80dcd9b93a8d914e4f1f6f1cda653ff

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest
-  digest: sha256:bdf89cdfb5b791d382184a7a769862b15c38e94e7d82b268c58d40d8952720f2
-# created: 2025-10-03T19:51:38.870830821Z
+  digest: sha256:da8a4a745d5eb96f07fa99a550afe49ac80dcd9b93a8d914e4f1f6f1cda653ff
+# created: 2025-10-14T15:58:07.94636513Z

.github/workflows/ci.yaml

@@ -12,7 +12,7 @@ jobs:
         node: [18, 20, 22, 24]
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: ${{ matrix.node }}
       - run: node --version
@@ -30,7 +30,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
       - run: node --version
@@ -44,7 +44,7 @@ jobs:
     runs-on: windows-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
       - run: npm install --engine-strict
@@ -55,7 +55,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
       - run: npm install
@@ -64,7 +64,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
       - run: npm install

.github/workflows/issues-no-repro.yaml

@@ -11,7 +11,7 @@ jobs:
       pull-requests: write
     steps:
       - uses: actions/checkout@v5
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v6
         with:
           node-version: 18
       - run: npm install