Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -417,7 +417,7 @@ If you need to recompute the lockfile in your PR, you can use:
 ```console
 $ # Update all the pinned dependencies in pyproject.toml & all versions in poetry.lock
 $ # (there are actually no pinned dependencies in pyproject.toml, so this only updates the
-$ # lockfile.
+$ # lockfile).
 $ poetry update
 
 $ # Similarly, update dependencies in the lockfile. In procrastinate, it's equivalent