Resolve "Node.js 16 actions are deprecated" warning.

.github/workflows/tests.yml

@@ -32,12 +32,12 @@ jobs:
     steps:
 
       - name: Clone repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: ${{ github.workspace }}/go/src/github.com/Psiphon-Labs/psiphon-tunnel-core
 
       - name: Install Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v4
         with:
           go-version: ${{ matrix.go }}