chore(npm): remove duplicated pcakage

Author: azu

package.json

@@ -38,7 +38,6 @@
     "espower-babel": "^4.0.0",
     "mocha": "^2.3.4",
     "power-assert": "^1.1.0",
-    "sentence-splitter": "^1.0.2",
     "textlint": "^5.0.2",
     "textlint-tester": "^0.4.0"
   },