Update xo

Author: wooorm

package.json

@@ -56,7 +56,7 @@
     "type-coverage": "^2.0.0",
     "typescript": "^4.0.0",
     "unist-util-remove-position": "^4.0.0",
-    "xo": "^0.39.0"
+    "xo": "^0.42.0"
   },
   "scripts": {
     "build": "rimraf \"{index,test}.d.ts\" && tsc && type-coverage",