update pr template checklist

Author: rmorshea

.github/pull_request_template.md

@@ -6,6 +6,6 @@ A summary of the changes.
 
 Please update this checklist as you complete each item:
 
-- [ ] Tests have been included for all bug fixes or new functionality.
-- [ ] The `changelog.rst` has been updated with any significant changes.
-- [ ] GitHub Issues which may be closed by this Pull Request have been linked.
+- [ ] Tests have been included if bugs were fixed or functionality was added.
+- [ ] The `changelog.rst` has been updated if there were significant changes.
+- [ ] Any relevant GitHub Issues have been linked to or marked for closure.