chore(npm): remove unnecessary module

Author: azu

package.json

@@ -41,7 +41,6 @@
   },
   "dependencies": {
     "kuromojin": "^1.0.1",
-    "sentence-splitter": "^1.0.1",
-    "structured-source": "^3.0.2"
+    "sentence-splitter": "^1.0.1"
   }
 }