Update cache epoch to match what production has used since August

webpack.config.js

@@ -26,7 +26,7 @@ const htmlWebpackPluginCommon = {
 };
 
 // When this changes, the path for all JS files will change, bypassing any HTTP caches
-const CACHE_EPOCH = 'gleba';
+const CACHE_EPOCH = 'pentapod';
 
 const base = {
     mode: process.env.NODE_ENV === 'production' ? 'production' : 'development',