[bug] do not declare VERSION twice

reverting a recent change that breaks `generate` step in build.

-Closes: #727

pkg/config/version/checknewer.go

@@ -11,9 +11,7 @@ import (
 
 const verURI = "https://downloads.leap.se/RiseupVPN/"
 
-var VERSION string
-
-// returns true if there's a newer version string published on the server
+// CanUpgrade returns true if there's a newer version string published on the server
 // this needs to manually bump latest version for every platform in the
 // downloads server.
 // at the moment, we hardcode RiseupVPN in the path, assuming that all clients