Make sure that a user MUST always tick the CHANGELOG entry.

Author: m-mohr

.github/pull_request_template.md

@@ -6,9 +6,8 @@
 1. 
 2. 
 
-
 **PR Checklist:**
 
 - [ ] This PR has breaking changes.
-- [ ] I have added my changes to the [CHANGELOG](https://github.com/radiantearth/stac-spec/blob/dev/CHANGELOG.md).
+- [ ] I have added my changes to the [CHANGELOG](https://github.com/radiantearth/stac-spec/blob/dev/CHANGELOG.md) **or** a CHANGELOG entry is not required.
 - [ ] API only: I have run `npm run generate-all` to update the [generated OpenAPI files](https://github.com/radiantearth/stac-spec/blob/dev/api-spec/README.md#openapi-definitions).