Use consistent context for the "Add New" string when referring to media

[SergeyBiryukov]

Background: #21391.

As of [21948], the built-in attachment post type is registered with this string as the add_new label:

_x( 'Add New', 'add new media' )

This is the only place in core where the add new media context is used. All the other instances of this string, including the admin menu, use the file context:

_x( 'Add New', 'file' )

As far as I can tell, there is no reason for the context of these strings to be different, and it seems like an oversight. For consistency, the former string should use the file context as well.

[tobifjellner]

Since this fix will remove one string without adding any new, it can safely be back-ported to 6.0.1, too :)

[benjgrolleau]

Hi there,
I've just changed on line 78, 'add new media' to 'file' as expected.

[SergeyBiryukov]

Replying to benjgrolleau:

I've just changed on line 78, 'add new media' to 'file' as expected.

Thanks for the patch! Looks great :)

Replying to tobifjellner:

Since this fix will remove one string without adding any new, it can safely be back-ported to 6.0.1, too :)

Yes, you're right. However, as it's not a regression in 6.0 and we generally try to minimize the number of changed files in minor releases due to ​reliability concerns for background updates, I think this can stay in 6.1 for now. If 6.0.1 ends up having any other changes in wp-includes/post.php, then this can be included as well.

[SergeyBiryukov]

In 53453:

I18N: Use consistent context for the "Add New" string when referring to media.

This replaces the only instance of the add new media context with file, used in other instances of the string.

Follow-up to [9198], [10680], [21948].

Props benjgrolleau, tobifjellner, SergeyBiryukov.
Fixes #55876.