Combine two code fences in README.md

Combine two adjacent code fences (each with a single command of the same programming language) into one code fence.

Left a blank line between the two commands to improve readability.

Author: mjbear

README.md

@@ -59,9 +59,7 @@ Open an elevated PowerShell window (as administrator) and paste the following tw
 
 ```powershell
 dism.exe /online /enable-feature /featurename:Microsoft-Windows-Subsystem-Linux /all /norestart
-```
 
-```powershell
 dism.exe /online /enable-feature /featurename:VirtualMachinePlatform /all /norestart
 ```