Build: update to GitHub Actions v5 to fix warnings

* Fix GitHub Actions noise about "Node.js 20 actions are deprecated."
  which is a pointless and confusing treadmill about internal primitives
  like "checkout" and "setup-node" which are not simple shell scripts
  but instead full containers that themselves utilize Node.js internally.
  No user should have to care about this, and the warnings ideally either
  would not exist, have a stable subset, or at the very least refer
  to the action/v4 being deprecated instead of confusing details
  about what those are internally made of.

* Remove lock file

Ref https://timotijhof.net/posts/2024/lockfiles-for-apps-not-packages-still/

Ref https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

Author: Krinkle

.github/workflows/test.yml

@@ -24,21 +24,18 @@ jobs:
 
     steps:
       - name: Clone repository
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           persist-credentials: false
 
       - name: Set up Node.js
-        uses: actions/setup-node@v4
+        uses: actions/setup-node@v5
         with:
           node-version: ${{ matrix.node }}
-          cache: npm
 
-      - name: Install npm dependencies
-        run: npm ci
+      - run: npm install
 
-      - name: Run tests
-        run: npm test
+      - run: npm test
 
       # We test multiple Windows shells because of prior stdout buffering issues
       # filed against Grunt. https://github.com/joyent/node/issues/3584