fix: generate requires terraform to be installed

Used to build the docs from schemas. Not all runners have terraform
installed, ensure it is available.

Author: hmlanigan

.github/workflows/build.yml

@@ -41,6 +41,10 @@ jobs:
         with:
           go-version-file: "go.mod"
           cache: true
+      - uses: hashicorp/setup-terraform@v3
+          with:
+            terraform_version: "1.9.*"
+            terraform_wrapper: false
       - run: go generate ./...
       - name: git diff
         run: |