Update appveyor.yml

it cannot cache if size larger than 1gb 
so delete unnecessary files

appveyor.yml

@@ -38,6 +38,8 @@ install:
     & "$steamCMDPath/steamcmd.exe" "+login anonymous" "+force_install_dir $steamData" "+app_update 298740" "+quit"
 
     $dataPath = $steamData.Replace("/", "\")
+    
+    Remove-Item -LiteralPath $dataPath\Content -Force -Recurse
 
     cmd /S /C mklink /J .\GameBinaries $dataPath\DedicatedServer64
 cache: