Replace section discussing CLA in the PR Template with DCO

Author: cppwfs

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,10 +1,10 @@
 Thank you for taking time to contribute this pull request!
 You might have already read the [contributor guide][1], but as a reminder, please make sure to:
 
-* Sign the [contributor license agreement](https://cla.pivotal.io/sign/spring)
 * Rebase your changes on the latest `main` branch and squash your commits
 * Add/Update unit tests as needed
 * Run a build and make sure all tests pass prior to submission
+* Sign-off commits according to the [Developer Certificate of Origin](https://spring.io/blog/2025/01/06/hello-dco-goodbye-cla-simplifying-contributions-to-spring)
 
 For more details, please check the [contributor guide][1].
 Thank you upfront!