docs: update the Heroku Deployment Guide for v4 (#549)

* Update Postgres config snippet

* Update Postgres config snippet debug flag

* Update localhost URLs to /developer-docs/ URL

* Remove the v4 contribution disclaimer

Co-authored-by: Pierre Wizla <[email protected]>

Author: bogdaaamn

docs/developer-docs/latest/setup-deployment-guides/deployment/hosting-guides/heroku.md

@@ -6,8 +6,6 @@ canonicalUrl: https://docs.strapi.io/developer-docs/latest/setup-deployment-guid
 
 # Heroku
 
-!!!include(developer-docs/latest/setup-deployment-guides/deployment/snippets/deployment-guide-not-updated.md)!!!
-
 This is a step-by-step guide for deploying a Strapi project on [Heroku](https://www.heroku.com/). Databases that work well with Strapi and Heroku are provided instructions on how to get started.
 
 ### Heroku Install Requirements
@@ -198,7 +196,7 @@ yarn add pg-connection-string
 
 #### 4. Create your Heroku database config file for production
 
-Create new subfolders in `./config` like so: `/env/production`, then create a new `database.js` in it (see [environment documentation](http://localhost:8080/documentation/developer-docs/latest/setup-deployment-guides/configurations/optional/environment.md)). Your path should look like this: `./config/env/production/database.js`. When you run locally you should be using the `./config/database.js` which could be set to use SQLite, however it's recommended you use PostgreSQL locally also, for information on configuring your local database, please see the [database documentation](/developer-docs/latest/setup-deployment-guides/configurations/required/databases.md).
+Create new subfolders in `./config` like so: `/env/production`, then create a new `database.js` in it (see [environment documentation](/developer-docs/latest/setup-deployment-guides/configurations/optional/environment.md)). Your path should look like this: `./config/env/production/database.js`. When you run locally you should be using the `./config/database.js` which could be set to use SQLite, however it's recommended you use PostgreSQL locally also, for information on configuring your local database, please see the [database documentation](/developer-docs/latest/setup-deployment-guides/configurations/required/databases.md).
 
 `Path: ./config/env/production/database.js`
 
@@ -207,25 +205,19 @@ const parse = require('pg-connection-string').parse;
 const config = parse(process.env.DATABASE_URL);
 
 module.exports = ({ env }) => ({
-  defaultConnection: 'default',
-  connections: {
-    default: {
-      connector: 'bookshelf',
-      settings: {
-        client: 'postgres',
-        host: config.host,
-        port: config.port,
-        database: config.database,
-        username: config.user,
-        password: config.password,
-        ssl: {
-          rejectUnauthorized: false,
-        },
-      },
-      options: {
-        ssl: true,
+  connection: {
+    client: 'postgres',
+    connection: {
+      host: config.host,
+      port: config.port,
+      database: config.database,
+      user: config.user,
+      password: config.password,
+      ssl: {
+        rejectUnauthorized: false
       },
     },
+    debug: false,
   },
 });
 ```
@@ -238,7 +230,7 @@ heroku config:set NODE_ENV=production
 
 #### 5. Create your Strapi server config for production
 
-Create a new `server.js` in a new [env](http://localhost:8080/documentation/developer-docs/latest/setup-deployment-guides/configurations/optional/environment.md) folder. In this file you only need one key, the `url`, to notify Strapi what our public Heroku domain is. All other settings will automatically be pulled from the default `./config/server.js`.
+Create a new `server.js` in a new [env](/developer-docs/latest/setup-deployment-guides/configurations/optional/environment.md) folder. In this file you only need one key, the `url`, to notify Strapi what our public Heroku domain is. All other settings will automatically be pulled from the default `./config/server.js`.
 
 `Path: ./config/env/production/server.js`