Use rvm default alias instead of pinned ruby version in ExecStart

sinatra.service

@@ -7,7 +7,7 @@ Type=simple
 User=randy
 Group=users
 WorkingDirectory=/opt/sinatra
-ExecStart=/home/randy/.rvm/bin/rvm ruby-4.0.5 do bundle exec ruby app.rb
+ExecStart=/home/randy/.rvm/bin/rvm default do bundle exec ruby app.rb
 Restart=on-failure
 
 [Install]