chore: upgrade spectron

fixes nklayman#467

Author: ekoeryanto

package.json

@@ -38,7 +38,7 @@
     "pumpify": "^1.5.1",
     "semver": "^6.0.0",
     "shebang-loader": "^0.0.1",
-    "spectron": "^7.0.0",
+    "spectron": "^8.0.0",
     "split2": "^3.0.0",
     "terser-webpack-plugin": "^1.1.0",
     "through2-filter": "^3.0.0",