Forms: Fix translation issue with %

[edanzer]

Fixes #19940

Proposed changes:

Fixes translation issue with __( 'Emptying Spam (%1$s%)', 'jetpack' ). The last % is a literal % that should render, but causes an error during translation because its perceived as an escaping character.

• Fix PHP issue: This if fixed by adding an extra % before the %. This fixes the PHP error.
• Fix JS issue (see related comment): the PHP fix causes a secondary issue. The string is later passed to JS. We replace the %1$s with a value, but leave %% in place and render it. To fix this new issue, in the same place, we also replace %% to %.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

None.

Does this pull request change what data or activity we track or use?

No.

Testing instructions:

• Go to a site with a form block, and generate a few form submissions from the front end.
• Go to the 'Feedback' page in the backend, and mark the submissions as spam.
• Go to the 'Feedback' > 'Spam' tab, and click the Empty Spam button at the end. Confirm the button text renders correctly as Emptying Spam (0%) (percentage may vary).
• Update your site to a foreign language, and re-run the test above to confirm the text string still renders correctly and spam is deleted.

[github-actions]

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[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the fix/spam-percent-translation branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack fix/spam-percent-translation
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
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