Update unicorn.py: Remove runtime error from obfuscation

[jeffmcjunkin]

Currently, the attempt to replace the wwww variable in the following line results in a runtime error from the PowerShell command (though it does still run the payload):

$wwww=$wwww.replace("$Win32", "%s");

Depending upon variable names, the error looks like the following as the first part of the output of the PowerShell command:

Method invocation failed because [System.RuntimeType] does not contain a method named 'replace'.
At line:1 char:2005
+ ... Yl" -names VJy;$BC=$BC.replace("VJy", "Win32Funct"+"i"+"ons");[byte[] ...
+                    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : MethodNotFound

This makes sense, as $wwww at that point is a type, not a string, so it doesn't have a .replace() function.

To fix this, I removed the above line entirely from the embedded powershell_code string, along with the ,Win32 in the % (msv,kernel,kernel,[...] end of the line.