Update PR template

Author: kfischer-okarin

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,13 +1,5 @@
+redmine.orgのチケットURL: https://www.redmine.org/issues/xxxx
 
-____________________________________________________________________
-
-Your contributions to Redmine are welcome!
-
-Please **open an issue on the [official website]** instead of sending pull requests.
-
-Since the development of Redmine is not conducted on GitHub but on the [official website] and core developers are not monitoring the GitHub repo, pull requests might not get reviewed.
-
-For more detail about how to contribute, please see the wiki page [Contribute] on the [official website].
-
-[official website]: https://www.redmine.org/
-[Contribute]: https://www.redmine.org/projects/redmine/wiki/Contribute
+TODO:
+- [ ] 単体テストかく
+- [ ] ...