Update terraform-linters/setup-tflint action to v6

Author: renovate[bot]

.github/workflows/ci.yml

@@ -63,7 +63,7 @@ jobs:
           path: ~/.tflint.d/plugins
           key: ${{ runner.os }}-tflint-${{ hashFiles('**/.tflint.hcl') }}
 
-      - uses: terraform-linters/setup-tflint@v4
+      - uses: terraform-linters/setup-tflint@v6
         name: Setup TFLint
         with:
           tflint_version: v0.51.2