Update install-ubuntu.md (#1275)

* Update install-ubuntu.md

Add a "apt upgrade" after the PPA is added.

* Update install-ubuntu.md

remove apt update after adding the PPA as it runs by default now.

---------

Co-authored-by: Aaron Honeycutt <aaron@system76.com>
Co-authored-by: Levi Portenier <levi@system76.com>

Author: 3 people

content/install-ubuntu.md

@@ -197,8 +197,8 @@ Once you've installed Ubuntu, you'll need to download and install the <u>System7
 
 ```bash
 sudo apt-add-repository -y ppa:system76-dev/stable
-sudo apt update
 sudo apt install system76-driver
+sudo apt upgrade
 ```
 
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