Update database config in The Rails Comamnd Line of guide [ci skip]

guides/source/command_line.md

@@ -645,13 +645,16 @@ $ cat config/database.yml
 # Configure Using Gemfile
 # gem 'pg'
 #
-development:
+default: &default
   adapter: postgresql
   encoding: unicode
+  # For details on connection pooling, see Rails configuration guide
+  # http://guides.rubyonrails.org/configuring.html#database-pooling
+  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+
+development:
+  <<: *default
   database: gitapp_development
-  pool: 5
-  username: gitapp
-  password:
 ...
 ...
 ```