Fix the wrong full documentation link (#14293)

.env.production.sample

@@ -2,7 +2,7 @@
 # with the `rake mastodon:setup` interactive setup wizard, but to customize
 # your setup even further, you'll need to edit it manually. This sample does
 # not demonstrate all available configuration options. Please look at
-# https://docs.joinmastodon/admin/config/ for the full documentation.
+# https://docs.joinmastodon.org/admin/config/ for the full documentation.
 
 # Federation
 # ----------