Improve 1.21 document for Database Preparation (#28643) (#28644)

Backport #28643

Fix #28247

Author: wxiaoguang

docs/content/installation/database-preparation.en-us.md

@@ -17,7 +17,9 @@ menu:
 
 # Database Preparation
 
-You need a database to use Gitea. Gitea supports PostgreSQL (>=10), MySQL (>=5.7), MariaDB, SQLite, and MSSQL (>=2008R2 SP3). This page will guide into preparing database. Only PostgreSQL and MySQL will be covered here since those database engines are widely-used in production. If you plan to use SQLite, you can ignore this chapter.
+You need a database to use Gitea. Gitea supports PostgreSQL (>= 12), MySQL (>= 8.0), MariaDB (>= 10.4), SQLite (builtin), and MSSQL (>= 2012 SP4). This page will guide into preparing database. Only PostgreSQL and MySQL will be covered here since those database engines are widely-used in production. If you plan to use SQLite, you can ignore this chapter.
+
+If you use an unsupported database version, please [get in touch](/help/support) with us for information on our Extended Support Contracts. We can provide testing and support for older databases and integrate those fixes into the Gitea codebase.
 
 Database instance can be on same machine as Gitea (local database setup), or on different machine (remote database).