Update actions/checkout action to v3 (#36)

Co-authored-by: Renovate Bot <bot@renovateapp.com>

Author: renovate[bot]

.github/workflows/pipeline.yml

@@ -6,15 +6,15 @@ jobs:
     container: hashicorp/terraform
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - run: terraform fmt -check -recursive -diff
 
   validate:
     runs-on: ubuntu-latest
     container: hashicorp/terraform
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Terraform Init
         run: terraform init
         working-directory: examples/test
@@ -27,7 +27,7 @@ jobs:
     container: hashicorp/terraform
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Terraform Init
         run: terraform init
         working-directory: examples/test
@@ -40,7 +40,7 @@ jobs:
     name: Show infracost diff
     steps:
       - name: Check out repository
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
       - name: Run infracost diff
         uses: infracost/infracost-gh-action@master
         env: