Avoid caching credits.php during development

[nacin]

credits.php has a 24-hour cache on the transient. The point of this cache is to speed up this page when accessed repeatedly in a narrow timeframe (such as right after an update, clicking between the various tabs). The credits API itself is also cached, and that can be flushed manually. But individuals updating their profiles (such as to see changes or ensure their name changes are reflected) have to wait for the local cache to refresh too, which is annoying when you're running a development version.

It would be easier if test installs did not bother to cache this data, and instead always did an HTTP request.

[nacin]

In 26872:

Always do an HTTP request on credits.php when running a development version of WordPress.

fixes #26727.