Docs: avoid confusing use of the word "synchronized"

Docs: avoid confusing use of the word "synchronized"

It's misleading to call the data directory the "synchronized data
directory" when discussing a crash scenario when using pg_rewind's
--no-sync option.  Here we just remove the word "synchronized" to avoid
any possible confusion.

Author: Justin Pryzby
Discussion: https://postgr.es/m/20220411020336.GB26620@telsasoft.com
Backpatch-through: 12, where --no-sync was added