add related metrolines to labels.json

Author: mniinio

src/data/method/en/labels.json

@@ -4,5 +4,6 @@
   "outcomes": "Outcomes",
   "how_it_works": "How it works",
   "steps": "Steps",
-  "apply_in_work": "Apply in your work"
-}
+  "apply_in_work": "Apply in your work",
+  "related_metrolines": "Related metrolines",
+}