Fix defer_build description

"CREATE INDEX is by default a synchronous operation. so every CREATE INDEX statement blocks until the operation finishes. Index building starts by creating a task that is queued for index build. After this phase, if you lose connectivity, the index build operation continues in the background. You can also run index creation asynchronously using the defer_build clause. In the asynchronous mode, CREATE INDEX starts a task to create the primary index and returns as soon as the task is queued for execution, and then the full index creation operation happens in the background."

needs to change to something like below:

"CREATE INDEX is by default a synchronous operation. so every CREATE INDEX statement blocks until the operation finishes. Index building starts by creating a task that is queued for index build. After this phase, if you lose connectivity, the index build operation continues in the background.

You can also run index creation asynchronously using the defer_build clause. After one or several indexes created using CREATE INDEX with defer_build clause, BUILD INDEX command needs to be executed. BUILD INDEX is an asynchronous operation. BUILD INDEX creates a task to build the primary or secondary GSI indexes and returns as soon as the task is queued for execution. The full index creation operation happen in the background."