In <https://jira.mongodb.org/browse/SERVER-101470>, I made the log timestamp format consistent between pre-server-configuration log messages and post-server-configuration log messages by setting both formats to "UTC".

This was a departure from the status quo at the time, which had the post-server-configuration default set to "local".

The change of default log timestamp format is potentially problematic for multiple reasons:

• Python <3.11 programs that parse timestamps using `datetime.datetime.fromisoformat` do not tolerate the trailing "Z" of the UTC format.
• Log ingestion tools, such as Filebeat, use regular expressions to extract portions of (admittedly JSON based) log messages.

Other issues might manifest as the format change makes its way into more software.

For these reasons, I'm going to change the post-server-configuration default log timestamp format back to "local".