[5.1] Update to include MariaDB and remove SQL Server in README (.txt and .md) (#43368)

Author: robertsilen

README.md

@@ -20,7 +20,7 @@ Overview
 What is Joomla?
 ---------------------
 * [Joomla!](https://www.joomla.org/about-joomla.html) is a **Content Management System** (CMS) which enables you to build websites and powerful online applications.
-* It is a simple and powerful web server application which 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).
+* It is a simple and powerful web server application which requires a server with PHP and either MySQL, MariaDB or PostgreSQL to run. You can find [full technical requirements here](https://downloads.joomla.org/technical-requirements).
 * Joomla! is **free and Open Source software** distributed under the GNU General Public License version 2 or later.
 
 Looking for an installable package?

README.txt

@@ -12,7 +12,7 @@ The Joomla! 5.1 branch is under heavy development and not all links in this docu
 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, MariaDB or PostgreSQL to run.
 	You can find full technical requirements here: https://downloads.joomla.org/technical-requirements.
 
 3- Is Joomla! for you?