fix: change import long to require (#620)

Source-Link: googleapis/synthtool@d229a12
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-nodejs:latest@sha256:74ab2b3c71ef27e6d8b69b1d0a0c9d31447777b79ac3cd4be82c265b45f37e5e

Author: gcf-owl-bot[bot]