fix(docs): remove npm package config override

This is no longer possible, as per [rfc
21](https://github.com/npm/rfcs/blob/latest/implemented/0021-reduce-lifecycle-script-environment.md)

PR-URL: #3485
Credit: @wraithgar
Close: #3485
Reviewed-by: @isaacs

docs/content/configuring-npm/package-json.md

@@ -549,12 +549,8 @@ had the following:
 }
 ```
 
-and then had a "start" command that then referenced the
-`npm_package_config_port` environment variable, then the user could
-override that by doing `npm config set foo:port 8001`.
-
-See [`config`](/using-npm/config) and [`scripts`](/using-npm/scripts) for
-more on package configs.
+It could also have a "start" command that referenced the
+`npm_package_config_port` environment variable.
 
 ### dependencies
 

docs/content/using-npm/scripts.md

@@ -245,41 +245,7 @@ package.json file, then your package scripts would have the
 in your code with `process.env.npm_package_name` and
 `process.env.npm_package_version`, and so on for other fields.
 
-#### configuration
-
-Configuration parameters are put in the environment with the
-`npm_config_` prefix. For instance, you can view the effective `root`
-config by checking the `npm_config_root` environment variable.
-
-#### Special: package.json "config" object
-
-The package.json "config" keys are overwritten in the environment if
-there is a config param of `<name>[@<version>]:<key>`.  For example,
-if the package.json has this:
-
-```json
-{
-  "name" : "foo",
-  "config" : {
-    "port" : "8080"
-  },
-  "scripts" : {
-    "start" : "node server.js"
-  }
-}
-```
-
-and the server.js is this:
-
-```javascript
-http.createServer(...).listen(process.env.npm_package_config_port)
-```
-
-then the user could change the behavior by doing:
-
-```bash
-  npm config set foo:port 80
-  ```
+See [`package-json.md`](/using-npm/package-json) for more on package configs.
 
 #### current lifecycle event