Update dependency mocha to v7

Author: renovate-bot

package-lock.json

@@ -66,7 +66,7 @@
     "eslint-plugin-prefer-let": "^1.0.1",
     "git-diff-apply": "0.22.0",
     "git-fixtures": "^2.1.0",
-    "mocha": "^6.0.0",
+    "mocha": "^7.0.0",
     "mocha-helpers": "^4.0.0",
     "renovate-config-standard": "^2.0.0",
     "sinon": "^8.0.0",