chore(deps): update dependency lint-staged to v15

Author: renovate[bot]

package.json

@@ -43,7 +43,7 @@
     "generate-changelog": "1.8.0",
     "husky": "0.14.3",
     "istanbul": "0.4.5",
-    "lint-staged": "7.3.0",
+    "lint-staged": "15.0.1",
     "mocha": "5.2.0",
     "nock": "10.0.6",
     "prettier-standard": "8.0.1"