Update lint-staged requirement to ^7.0.0 (#9519)

Updates the requirements on [lint-staged](https://github.com/okonet/lint-staged) to permit the latest version.
- [Release notes](https://github.com/okonet/lint-staged/releases)
- [Commits](https://github.com/okonet/lint-staged/commits/v7.0.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>

package.json

@@ -127,7 +127,7 @@
     "immutability-helper": "^2.5.0",
     "jest": "^21.1.0",
     "jsonml.js": "^0.1.0",
-    "lint-staged": "^6.0.0",
+    "lint-staged": "^7.0.0",
     "lz-string": "^1.4.4",
     "majo": "^0.4.1",
     "mockdate": "^2.0.1",