correct documentation for WP_User_Request class

[pbiron]

In the DocBlocks for the properties of the class, the @since tags are missing and the @type tags for $email, $confirmed_timestamp and $completed_timestamp props are wrong:

• $email should be type string
• the other 2 should be type int|null

[garrett-eclipse]

Thanks @pbiron this looks good. @SergeyBiryukov beat me to milestoning and owning so I'll let him finish reviewing, but this looks good to commit in my view.

[garrett-eclipse]

Oops didn't mean to unmilestone it, should have refreshed before submitting.

[SergeyBiryukov]

In 47494:

Docs: Add missing @since tags for WP_User_Request properties.

Correct type for $email, $confirmed_timestamp, and $completed_timestamp properties.

Props pbiron, garrett-eclipse.
Fixes #49675.

[garrett-eclipse]

Dropping privacy focus as it's already in the Privacy component.