ci: bump actions/setup-node from 4 to 7 (#73)

Same bump as Dependabot's PR #63, applied by hand: that PR edited the
same ci.yml lines as the actions/checkout bump and conflicted once
checkout landed first.

Author: renezander030

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     name: test (Node ${{ matrix.node }})
     steps:
       - uses: actions/checkout@v7
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: ${{ matrix.node }}
           cache: npm
@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v7
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: '20'
           cache: npm
@@ -44,7 +44,7 @@ jobs:
     name: platform smoke (${{ matrix.os }})
     steps:
       - uses: actions/checkout@v7
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@v7
         with:
           node-version: '20'
           cache: npm