Update PULL_REQUEST_TEMPLATE.md (#2744)
Update PULL_REQUEST_TEMPLATE.md (#2744)

Fixes #issue

> It's a good idea to open an issue first for discussion.

- [ ] `pom.xml` parent set to latest `shared-configuration`
- [ ] Appropriate changes to README are included in PR
- [ ] API's need to be enabled to test (tell us)
- [ ] Environment Variables need to be set (ask us to set them)
- [ ] Tests pass (`mvn -P lint clean verify`)
  * (Note- `Checkstyle` passing is required; `Spotbugs`, `ErrorProne`, `PMD`, etc. `ERROR`'s are advisory only)
- [x] Please **Merge** after approval.

GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples,GoogleCloudPlatform/java-docs-samples