Fix changelog script to work with pyproject.toml

Author: nikhilwoodruff

Makefile

@@ -27,6 +27,6 @@ documentation:
 changelog:
 	build-changelog changelog.yaml --output changelog.yaml --update-last-date --start-from 0.1.0 --append-file changelog_entry.yaml
 	build-changelog changelog.yaml --org PolicyEngine --repo openfisca-uk --output CHANGELOG.md --template .github/changelog_template.md
-	bump-version changelog.yaml setup.py
+	bump-version changelog.yaml pyproject.toml
 	rm changelog_entry.yaml || true
 	touch changelog_entry.yaml