doc: update the default of data checksums in the doc of pg_rewind

[Zhijie Hou (Fujitsu)]

Hi,

I noticed that the pg_rewind documentation still states that data
checksums is disabled by default, but it has been changed to on since PG18.

Here's a small patch to update this.

Best Regards,
Hou zj

v1-0001-Fix-outdated-doc-in-pg_rewind.patch
Description: v1-0001-Fix-outdated-doc-in-pg_rewind.patch