ci: pass LITELLM_LICENSE to e2e_ui_testing proxy

Key regeneration is an enterprise feature — without LITELLM_LICENSE the
endpoint returns a 403 and the Playwright test for "Regenerate key"
never sees the success view. Other CircleCI jobs already pass this
secret; the e2e_ui_testing job was missing it.

.circleci/config.yml

@@ -3201,6 +3201,7 @@ jobs:
           name: Start LiteLLM proxy
           environment:
             LITELLM_MASTER_KEY: "sk-1234"
+            LITELLM_LICENSE: ${LITELLM_LICENSE}
             MOCK_LLM_URL: "http://127.0.0.1:8090/v1"
             DISABLE_SCHEMA_UPDATE: "true"
             SERVER_ROOT_PATH: ""