Remove unused dev dependencies

Follow up to #1269

Author: leebyron

package.json

@@ -56,8 +56,6 @@
     "beautify-benchmark": "0.2.4",
     "benchmark": "2.1.4",
     "chai": "4.1.2",
-    "chai-json-equal": "0.0.1",
-    "chai-spies-next": "0.9.3",
     "chai-subset": "1.6.0",
     "coveralls": "3.0.0",
     "eslint": "4.17.0",