Bump actions/checkout from 2 to 3 (#45)

Author: dependabot[bot]

.github/workflows/test.yml

@@ -56,7 +56,7 @@ jobs:
         use_lua: yes
     - name: Install apt dependencies.
       run: sudo apt-get install -y lua-json
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v3
       with:
         submodules: recursive
     - name: Install haproxy-lua-http globally.