Update README.md to include MariaDB (#43343)

* Update README.md to include MariaDB

README.txt

@@ -9,7 +9,7 @@ Joomla! CMS™
 2- What is Joomla?
 	* Joomla! is a Content Management System (CMS) which enables you to build websites and powerful online applications.
 	* It's a free and Open Source software, distributed under the GNU General Public License version 2 or later.
-	* This is a simple and powerful web server application and it requires a server with PHP and either MySQL, PostgreSQL or SQL Server to run.
+	* This is a simple and powerful web server application and it requires a server with PHP and either MySQL or PostgreSQL to run.
 	You can find full technical requirements here: https://downloads.joomla.org/technical-requirements.
 
 3- Is Joomla! for you?