Update publishing key; try to get symbol packages publishing again

Author: nblumhardt

appveyor.yml

@@ -12,8 +12,7 @@ skip_commits:
 deploy:
 - provider: NuGet
   api_key:
-    secure: JAnOxPQMZRp8ousbAW4vYnVtd936AOMp4gDGucCQ1RZrDZW3J+X5QmbLO7OJKtBr
-  skip_symbols: true
+    secure: wm1N2hx6N0X0f4bae55X83isfINQNHyZkkR1mA/4XIdOJYEDKVonwQrxdgWxwGgl
   on:
     branch: /^(master|dev)$/
 - provider: GitHub