Revert "chore: upgrade to node 18"

[feanil]

Reverts #34311

Failing paver assets build:

TASK [edxapp : gather static assets with paver and pull translations] **********
fatal: [10.4.11.211]: FAILED! => {
    "changed": true,
    "cmd": [
        "/edx/bin/edxapp-update-assets"
    ],
    "delta": "0:00:16.132696",
    "end": "2024-04-09 16:53:18.010833",
    "rc": 1,
    "start": "2024-04-09 16:53:01.878137"
}

STDOUT:

---> pavelib.assets.update_assets
---> pavelib.prereqs.install_node_prereqs
NO_PREREQ_INSTALL is set, not installing prereqs
---> pavelib.prereqs.install_python_prereqs
NO_PREREQ_INSTALL is set, not installing prereqs
---> pavelib.assets.webpack
python manage.py lms --settings=production print_setting STATIC_ROOT WEBPACK_CONFIG_PATH 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log
python manage.py cms --settings=production print_setting STATIC_ROOT 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log
python manage.py cms --settings=production print_setting JS_ENV_EXTRA_CONFIG 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log --json
NODE_ENV=production STATIC_ROOT_LMS=/edx/var/edxapp/staticfiles STATIC_ROOT_CMS=/edx/var/edxapp/staticfiles/studio JS_ENV_EXTRA_CONFIG="{}" webpack --config=webpack.prod.config.js


Captured Task Output:
---------------------

---> pavelib.assets.update_assets
---> pavelib.prereqs.install_node_prereqs
---> pavelib.prereqs.install_python_prereqs
---> pavelib.assets.webpack
python manage.py lms --settings=production print_setting STATIC_ROOT WEBPACK_CONFIG_PATH 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log
python manage.py cms --settings=production print_setting STATIC_ROOT 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log
python manage.py cms --settings=production print_setting JS_ENV_EXTRA_CONFIG 2>/edx/app/edxapp/edx-platform/test_root/log/print_settings.log --json
NODE_ENV=production STATIC_ROOT_LMS=/edx/var/edxapp/staticfiles STATIC_ROOT_CMS=/edx/var/edxapp/staticfiles/studio JS_ENV_EXTRA_CONFIG="{}" webpack --config=webpack.prod.config.js

Build failed running pavelib.assets.update_assets: Subprocess return code: 2

[webpack-cli] Failed to load '/edx/app/edxapp/edx-platform/webpack.prod.config.js' config
[webpack-cli] TypeError: webpack.optimize.UglifyJsPlugin is not a constructor
    at Object.<anonymous> (/edx/app/edxapp/edx-platform/webpack.prod.config.js:26:13)
    at Module._compile (node:internal/modules/cjs/loader:1364:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1422:10)
    at Module.load (node:internal/modules/cjs/loader:1203:32)
    at Module._load (node:internal/modules/cjs/loader:1019:12)
    at Module.require (node:internal/modules/cjs/loader:1231:19)
    at require (node:internal/modules/helpers:177:18)
    at WebpackCLI.tryRequireThenImport (/edx/app/edxapp/edx-platform/node_modules/webpack-cli/lib/webpack-cli.js:223:30)
    at loadConfigByPath (/edx/app/edxapp/edx-platform/node_modules/webpack-cli/lib/webpack-cli.js:1406:38)
    at /edx/app/edxapp/edx-platform/node_modules/webpack-cli/lib/webpack-cli.js:1460:88

We're still investigating so might not need this but getting it ready just in-case.

[dianakhuang]

We were seeing issues with XBlock rendering with these changes.

Uncaught TypeError: Cannot read properties of undefined (reading 'prototype')
    at lms-application.e137e602d358.js:1:3845
    at constructBlock (lms-application.e137e602d358.js:1:3872)
    at initializeBlock (lms-application.e137e602d358.js:1:4505)
    at HTMLDivElement.<anonymous> (lms-application.e137e602d358.js:1:2921)
    at lms-main_vendor.5fc10bc4905c.js:1:1314
    at Function.map (lms-main_vendor.5fc10bc4905c.js:1:4947)
    at jQuery.fn.init.map (lms-main_vendor.5fc10bc4905c.js:1:1272)
    at initializeBlockLikes (lms-application.e137e602d358.js:1:2891)
    at Object.initializeXBlocks (lms-application.e137e602d358.js:1:4828)
    at initializeBlock (lms-application.e137e602d358.js:1:4311)

Something about the new webpack config is not loading XBlockToXModuleShim correctly, which breaks the loading of several XBlocks, including videos.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX staging environment in preparation for a release to production.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.

[edx-pipeline-bot]

2U Release Notice: This PR has been deployed to the edX production environment.