Updated deprecated rake task call

Author: koelle25

README.md

@@ -42,7 +42,7 @@ The initial authors of the plugin are [Emiliano Heyns](mailto:emiliano.heyns@gma
 4. Run the following commands to upgrade your database (make a database backup before):  
 
         bundle exec rake db:migrate RAILS_ENV=production
-        bundle exec rake db:migrate_plugins RAILS_ENV=production
+        bundle exec rake redmine:plugins:migrate RAILS_ENV=production
 
 5. Restart Redmine.
 
@@ -111,4 +111,4 @@ Danil Tashkinov, [github.com/nodecarter](https://github.com/nodecarter)
 
 ## Thanks to
 
-* https://github.com/jkraemer
+* https://github.com/jkraemer