fixed messed up appveyor.yml

Author: stesee

appveyor.yml

@@ -1,11 +1,12 @@
 version: 1.2.{build}
 image: Visual Studio 2017
 configuration: Release
+before_build:
 - ps: >-
     nuget restore
 
-    . "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.2 Tools\x64\sn.exe" -k ./MencoderSharp/MencoderSharp.snk
-build:
+    . "C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.7.2 Tools\x64\sn.exe" -k ./PdfAValidator/PdfAValidator.snk
+sbuild:
   verbosity: minimal
 artifacts:
 - path: '**\Mencoder*.nupkg'