Removed information about creating database[ci skip]

- As default index page is no longer in public folder, rails hits the
  welcome controller in railties for index action
- If the database is not created or username and password are
  incorrect in database.yml, those errors are first shown before index
  action succeeds
- welcome#index succeeds iff the database is created with correct
  details in database.yml
- So this information about creating database is not required in the
  index template
Merge pull request #11515 from prathamesh-sonpatki/edit-index-page

Removed information about creating database [ci skip]