Contact Form: add missing textdomain

[jeherve]

Proposed changes:

Follow-up to #34173

The textdomain is mandatory when declaring a new script; let's add it here to avoid warnings in our logs.

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

Epic: #33853

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

• No

Testing instructions:

• Open your error logs
• Go to the feedback menu in wp-admin
• Note the errors filling in your logs.
• Apply this branch.
• Refresh the page; no new errors should appear.

[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/contact-form-a11y-script-textdomain branch.

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

  bin/jetpack-downloader test jetpack fix/contact-form-a11y-script-textdomain
  

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.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Team Review, ...).
  
• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

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Once your PR is ready for review, check one last time that all required checks appearing at the bottom of this PR are passing or skipped.
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[anomiex]

The changes from #34520 that this was fixing were reverted in #34583. Details in p1702319188883389-slack-CBG1CP4EN.