Remove isDev flag

We can pretty much test everything here on self-hosted cloudrons now

src/config.js

@@ -32,7 +32,6 @@ exports = module.exports = {
     appFqdn: appFqdn,
     zoneName: zoneName,
 
-    isDev: isDev,
     isDemo: isDemo,
 
     tlsCert: tlsCert,
@@ -204,10 +203,6 @@ function database() {
     return get('database');
 }
 
-function isDev() {
-    return /dev/i.test(get('boxVersionsUrl'));
-}
-
 function isDemo() {
     return get('isDemo') === true;
 }