Revert "Use corepack"

This reverts commit 3cd3972.

.gitignore

@@ -14,7 +14,6 @@ pickle-email-*.html
 ## Environment normalisation:
 /.bundle
 /vendor/bundle
-/.yarn
 
 # these should all be checked in to normalise the environment:
 # Gemfile.lock, .ruby-version, .ruby-gemset

Dockerfile

@@ -12,7 +12,6 @@ RUN apk add zip
 
 RUN mkdir --parents /.prxci
 
-RUN corepack enable
 ADD ./package.json .
 RUN yarn install
 

package.json

@@ -4,7 +4,6 @@
   "description": "This service is built on Amazon's API Gateway and AWS Lambda. When deploying the Lambda function code, the secret key ID must be inserted for the service to work correctly. That key is kept in LastPass.",
   "main": "index.js",
   "type": "module",
-  "packageManager": "[email protected]",
   "engines": {
     "node": ">= 20.0.0"
   },
@@ -18,6 +17,7 @@
   "keywords": [],
   "author": "",
   "license": "AGPL-3.0",
+  "private": "true",
   "bugs": {
     "url": "https://github.com/PRX/upload.prx.org/issues"
   },