Update Postgres version in doc strings.

Author: knadh

README.md

@@ -2,7 +2,7 @@
 
 [![listmonk-logo](https://user-images.githubusercontent.com/547147/231084896-835dba66-2dfe-497c-ba0f-787564c0819e.png)](https://listmonk.app)
 
-listmonk is a standalone, self-hosted, newsletter and mailing list manager. It is fast, feature-rich, and packed into a single binary. It uses a PostgreSQL (⩾ v9.4) database as its data store.
+listmonk is a standalone, self-hosted, newsletter and mailing list manager. It is fast, feature-rich, and packed into a single binary. It uses a PostgreSQL (⩾ 12) database as its data store.
 
 [![listmonk-dashboard](https://user-images.githubusercontent.com/547147/134939475-e0391111-f762-44cb-b056-6cb0857755e3.png)](https://listmonk.app)
 

docs/docs/content/installation.md

@@ -1,6 +1,6 @@
 # Installation
 
-listmonk requires Postgres ⩾ v9.4.
+listmonk requires Postgres ⩾ 12.
 
 ## Binary
 - Download the [latest release](https://github.com/knadh/listmonk/releases) and extract the listmonk binary.

docs/site/layouts/index.html

@@ -152,7 +152,7 @@ <h2>Performance</h2>
       Multi-threaded, high-throughput, multi-SMTP e-mail queues.
       Throughput and sliding window rate limiting for fine grained control.  
       Single binary application with nominal CPU and memory footprint that runs everywhere.
-      The only dependency is a Postgres (⩾ v9.4) database.
+      The only dependency is a Postgres (⩾ 12) database.
     </p>
   </section>