Fix GitHub Actions by using stable action tags

Replace SHA-based action references with stable version tags:
- actions/setup-node@60edb5dd... → @v4
- shivammathur/setup-php@e6f75134... → @v2

This resolves "action could not be found at URI" errors caused by
GitHub API issues when resolving specific commit SHAs.

🤖 Generated with [Qoder][https://qoder.com]

.github/workflows/wordpress-tests.yml

@@ -26,7 +26,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: Setup Node.js
-      uses: actions/setup-node@60edb5dd545a775178f52524a9de5299b6d2bbed # v4.0.2
+      uses: actions/setup-node@v4
       with:
         node-version: ${{ matrix.node-version }}
         cache: 'npm'
@@ -60,7 +60,7 @@ jobs:
     - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
 
     - name: Setup Node.js
-      uses: actions/setup-node@60edb5dd545a775178f52524a9de5299b6d2bbed # v4.0.2
+      uses: actions/setup-node@v4
       with:
         node-version: '20'
         cache: 'npm'