Docs: Added the `locale` field to description for insert_user_meta filter.

[tmatsuur]

Since there was an anxious part in the source code of wp_insert_user function, I will post it.

In version 4.7, the insert_user_meta filter corresponds to the locale field, but this document does not describe it.

I think that it is better to correct the document.

[desrosj]

Thanks for catching this, @tmatsuur!

Looks like the locale user meta field was introduced in [38705] for version 4.7 and the filter documentation was just missed.

I don't think we need to add a @since annotation because no parameters were added to the filter, just possible values within the $meta array. I can change that when I commit.

[desrosj]

In 45479:

Docs: Add missing documentation for the locale meta field.

The user’s locale is passed in the $meta parameter for insert_user_meta. Added in [38705].

Props tmatsuur.
Fixes #47423.

[tmatsuur]

Replying to desrosj:

I don't think we need to add a @since annotation because no parameters were added to the filter, just possible values within the $meta array. I can change that when I commit.

Thanks @desrosj

In such cases, I did not know that @ since is unnecessary. I want to be careful in the future.