Update taxonomy.json

taxonomy.json

@@ -251,11 +251,7 @@
             {"name": "Writing and Editing Revisions"},
             {"name": "Lyrics Generation"},
             {"name": "Poetry Generation"},
-            {"name": "Text Style Transfer",
-            "children": [
-                {"name": "Text Style Transfer for Formality and Content"}
-                ]
-            },
+            {"name": "Text Style Transfer"},
             {"name": "Text Simplification"},
             {"name": "Data-to-Text Generation"},
             {"name": "Table-to-Text Generation"},