Update pull_request_template.md

Fixed CHANGELOG link to point the new repo

Author: keul

.github/pull_request_template.md

@@ -9,4 +9,4 @@
 - [ ] `pre-commit` hooks pass locally
 - [ ] Tests pass (run `make test`)
 - [ ] Documentation has been updated to reflect changes, if applicable, and docs build successfully (run `make docs`)
-- [ ] Changes are added to the [CHANGELOG](https://github.com/stac-utils/stac-fastapi/blob/main/CHANGES.md).
+- [ ] Changes are added to the [CHANGELOG](https://github.com/stac-utils/stac-fastapi-sqlalchemy/blob/main/CHANGES.md).