task: execute terraform from a proper directory

Part of #1631

[skip ci]

Author: php-coder

.github/workflows/provision-by-terraform.yml

@@ -55,7 +55,9 @@ jobs:
         run: tfenv --version
 
       - name: Run terraform init
+        working-directory: infra/terraform
         run: terraform init
 
       - name: Run terraform plan
+        working-directory: infra/terraform
         run: terraform plan