Remove old eslint files

This won't be picked up by our current eslint version

build/builtin/.eslintrc

@@ -1,20 +0,0 @@
-{
-	"env": {
-		"node": true,
-		"es6": true,
-		"browser": true
-	},
-	"rules": {
-		"no-console": 0,
-		"no-cond-assign": 0,
-		"no-unused-vars": 1,
-		"no-extra-semi": "warn",
-		"semi": "warn"
-	},
-	"extends": "eslint:recommended",
-	"parserOptions": {
-		"ecmaFeatures": {
-			"experimentalObjectRestSpread": true
-		}
-	}
-}