fix: translation string

[Soare-Robert-Daniel]

Summary

Changes:

• add missing translator comments
• add localization for upgrade URLs

Will affect visual aspect of the product

YES/NO

Screenshots

Test instructions

• Check if the strings and upgrade URL are in the correct format.

Check before Pull Request is ready:

• I have written a test and included it in this PR
• I have run all tests and they pass
• The code passes when running the PHP CodeSniffer
• Code meets WordPress Coding Standards for PHP, HTML, CSS and JS
• Security and Sanitization requirements have been followed
• I have assigned a reviewer or two to review this PR (if you're not sure who to assign, we can do this step for you)

Closes #978

[pirate-bot]

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