ci: Add missing environment variable to integration-test

Author: simonjbeaumont

.github/workflows/pull_request.yml

@@ -36,6 +36,8 @@ jobs:
             matrix_linux_command: "apt-get update -yq && apt-get install -yq jq && ./scripts/run-integration-test.sh"
             matrix_linux_5_8_enabled: false
             matrix_linux_nightly_main_enabled: false
+        env:
+            SWIFT_OPENAPI_GENERATOR_REPO_URL: file:///code
 
     compatibility-test:
       name: Compatibility test