Update lint-staged to the latest version 🚀 (firefox-devtools#5489)

Author: greenkeeper[bot]

package.json

@@ -136,7 +136,7 @@
     "jest-junit-reporter": "^1.1.0",
     "jest-localstorage-mock": "^2.2.0",
     "jest-serializer-babel-ast": "^0.0.5",
-    "lint-staged": "^6.0.1",
+    "lint-staged": "^7.0.0",
     "mochii": "^0.0.25",
     "mock-require": "^3.0.0",
     "node-emoji": "^1.8.1",