Change mastodon:webpush:generate_vapid_key task to not require functional env (#17338)

Fixes #17297

lib/tasks/mastodon.rake

@@ -441,7 +441,7 @@ namespace :mastodon do
 
   namespace :webpush do
     desc 'Generate VAPID key'
-    task generate_vapid_key: :environment do
+    task :generate_vapid_key do
       vapid_key = Webpush.generate_key
       puts "VAPID_PRIVATE_KEY=#{vapid_key.private_key}"
       puts "VAPID_PUBLIC_KEY=#{vapid_key.public_key}"