remove incorrect link in pr template

Author: philvarner

.github/pull_request_template.md

@@ -10,4 +10,4 @@
 
 - [ ] Code is formatted
 - [ ] Tests pass
-- [ ] Changes are added to the [CHANGELOG](https://github.com/stac-utils/pystac-api-client/blob/main/CHANGELOG.md)
+- [ ] Changes are added to CHANGELOG.md