Fix vale error

Author: nlarew

source/installation/install-on-a-local-machine/install-ubuntu.txt

@@ -5,7 +5,7 @@ Install on Ubuntu
 =================
 
 .. meta::
-   :description: Install Relational Migrator on Ubuntu by downloading the `.deb` binary, installing it, and optionally adding drivers such as MySQL or Oracle.
+   :description: Install Relational Migrator on Ubuntu by downloading the `.deb` binary, installing it, and optionally adding drivers such as MySQL, or Oracle.
 
 .. contents:: On this page
    :local: