docs(CHANGES): Fix highlighting

Author: tony

CHANGES

@@ -39,7 +39,7 @@ _Maintenance only, no bug fixes or new features_
   Per [Poetry's docs on managing dependencies] and `poetry check`, we had it wrong: Instead of using extras, we should create these:
 
   ```toml
-  [tool.poetry.group.[group-name].dependencies]
+  [tool.poetry.group.group-name.dependencies]
   dev-dependency = "1.0.0"
   ```