chore: Align heading level in Deploy an Operating System update

Step 1 should be h2, just like Prerequisites and other steps.

Ticket: none
Changelog: none
Signed-off-by: Vratislav Podzimek <[email protected]>

Author: vpodzime

01.Get-started/03.Deploy-an-operating-system-update/docs.md

@@ -24,7 +24,7 @@ You should:
 * know the IP address of your device
 
 
-### Step 1 - Download the mender-artifact utility on your workstation
+## Step 1 - Download the mender-artifact utility on your workstation
 
 !!! The simplest installation instructions for `mender-artifact` are covered below, see
 !!! [Downloads](../../11.Downloads/docs.md#mender-artifact) for installation alternatives such as