Remove requirement to update changelog from PR template.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,10 +1,9 @@
 <!--
-Please tick when you have done these. They don't need to all be completed before the PR is created.
+Please tick when you have done these. They don't need to all be completed before the PR is submitted.
 Delete them if they are not appropriate for this pull request.
 -->
 - [ ] I have provided code that clearly demonstrates the bug and that only works correctly when applying this fix
 - [ ] I have added suitable tests demonstrating a fixed bug or new/changed feature to the test suite in `tests/`
-- [ ] I have added a suitable explanation of the change to `CHANGELOG.md`
 - [ ] I have properly documented new or changed features in the documentation or in the docstrings
 - [ ] I have properly explained unusual or unexpected code in the comments around it
 - [ ] I have formatted my code using `black -t py36`