Fix runner: use CONFIG_FILE env var instead of command override

The command override bypasses the entrypoint that handles
registration. Use CONFIG_FILE env var which the entrypoint
respects, keeping the registration flow intact.

infra/kubernetes/platform/gitea-runner/deployment.yaml

@@ -18,8 +18,9 @@ spec:
       containers:
         - name: runner
           image: gitea/act_runner:latest
-          command: ["act_runner", "daemon", "--config", "/config/config.yaml"]
           env:
+            - name: CONFIG_FILE
+              value: /config/config.yaml
             - name: GITEA_INSTANCE_URL
               value: http://gitea-helm-http.platform.svc:3000
             - name: GITEA_RUNNER_REGISTRATION_TOKEN