update PR template to reflect new JIRA project

This is very overdue!

Author: jmtd

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,8 +2,9 @@ Thanks for submitting your Pull Request!
 
 Please make sure your PR meets the following requirements:
 
-- [ ] Pull Request title is properly formatted: `[CLOUD-XYA] Subject`
-- [ ] Pull Request contains link to the JIRA issue
+- [ ] A JIRA issue must exist in the OPENJDK project at issues.redhat.com
+- [ ] Pull Request title should be prefixed with the JIRA issue: `[OPENJDK-XYZ] Subject`
+- [ ] Pull Request contains hyperlink to the JIRA issue
 - [ ] Pull Request contains description of the issue
 - [ ] Pull Request does not include fixes for issues other than the main ticket
 - [ ] Attached commits represent units of work and are properly formatted