Troubleshoot the check release workflow (#1208)

* Use node 14 in the check release workflow

* Drop the `prepare` scripts

Author: jtpio

packages/jupyterlab-preview/package.json

@@ -40,7 +40,6 @@
     "clean": "jlpm run clean:lib && jlpm run clean:labextension",
     "clean:labextension": "rimraf ../../voila/labextension",
     "clean:lib": "rimraf lib tsconfig.tsbuildinfo",
-    "prepare": "jlpm run clean && jlpm run build:prod",
     "test": "jest",
     "watch": "run-p watch:src watch:labextension",
     "watch:labextension": "jupyter labextension watch .",

packages/voila/package.json

@@ -50,7 +50,6 @@
     "build:prod": "npm run build:lib && webpack --production",
     "clean": "jlpm run clean:lib",
     "clean:lib": "rimraf lib tsconfig.tsbuildinfo",
-    "prepare": "npm run build:lib && webpack",
     "test": "echo \"Error: no test specified\" && exit 1",
     "watch": "npm-run-all -p watch:*",
     "watch:lib": "tsc -w",