fix build: downgrade electron-builder

Author: timsuchanek

packages/graphql-playground-electron/package.json

@@ -136,7 +136,7 @@
     "concurrently": "3.5.1",
     "css-loader": "0.28.9",
     "electron": "1.8.4",
-    "electron-builder": "20.8.0",
+    "electron-builder": "19.55.3",
     "electron-devtools-installer": "2.2.3",
     "extract-text-webpack-plugin": "3.0.2",
     "file-loader": "1.1.6",