⬆️ update GitHub Actions to latest versions

- Upgrade actions/setup-go from v2/v4 (depending on workflow) to latest stable version
- Update all actions/checkout from v3/v4 (depending on workflow) to latest stable version
- Clean up outdated go.sum entries for buger/jsonparser v1.1.x

.github/workflows/obitest.yml

@@ -10,10 +10,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: Setup Go
-      uses: actions/setup-go@v2
+      uses: actions/setup-go@v5
       with:
         go-version: '1.23'
     - name: Checkout obitools4 project
-      uses: actions/checkout@v4
+      uses: actions/checkout@v5
     - name: Run tests
       run: make githubtests