Disambiguate "Cover" translatable string in the context of background-panel.js

[audrasjb]

Description

In image block's background-panel.js context, there is a "Cover" string sharing its translation with other occurrences of "Cover", like the Cover block. It results in wrong translation of the setting in some locales, like in French where the Cover Block is translated into "Bloc Bannière" while "Cover Size" cannot be translated into "Taille Bannière".

I'd recommend to add some context using _x(), just like we did in this other occurrence of "Cover", in a very similar context.

Step-by-step reproduction instructions

1. Install fr_FR language pack
2. Open background panel component
3. See that the "Cover" string is translated into "Bannière". "Couvrir" should be used instead.

Screenshots, screen recording, code snippet

Environment info

No response

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes

[audrasjb]

Ah and props to @jennydupuy for finding this issue on the French WordPress Slack team :)

[narenin]

@audrasjb I am working on this.

[narenin]

Hi @audrasjb, I have submitted the PR with fix, could you please check.

[ramonjd]

Good find @audrasjb, and thanks for the PR @narenin

I've left a couple of comments on the PR. Once those are addressed LGTM

[narenin]

@ramonjd Thanks for the feedback, I have implemented the same.