docs: add git on Ubuntu installation for better DX

If I just follow all the steps from docs in a fresh installation of Ubuntu and when I try to run `rails new myapp` I receive an error because git is not installed, so if I'm following this tutorial to get started with rails maybe we can assume that I need to install git to use this afterwards.

Author: iaurg

guides/source/install_ruby_on_rails.md

@@ -57,7 +57,7 @@ Open Terminal and run the following commands:
 ```bash
 # Install dependencies with apt
 $ sudo apt update
-$ sudo apt install build-essential rustc libssl-dev libyaml-dev zlib1g-dev libgmp-dev
+$ sudo apt install build-essential rustc libssl-dev libyaml-dev zlib1g-dev libgmp-dev git
 
 # Install Mise version manager
 $ curl https://mise.run | sh