Update actions/checkout action to v4 (#27)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/pipeline.yml

@@ -19,7 +19,7 @@ jobs:
     container: hashicorp/terraform
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Terraform Format Check
         run: terraform fmt -check -recursive -diff
 
@@ -32,7 +32,7 @@ jobs:
       }
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Terraform Init
         run: terraform init -upgrade
         working-directory: ${{ matrix.dir }}
@@ -56,7 +56,7 @@ jobs:
           - 4566:4566
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Terraform Init
         run: terraform init -upgrade
         working-directory: ${{ matrix.dir }}
@@ -73,7 +73,7 @@ jobs:
       }
     steps:
       - name: Check out repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Run infracost diff
         uses: infracost/infracost-gh-action@master
         env: