Fix edge case for 1 PM when editing

[porter-stripe]

Summary

• Don't use plural when only 1 PM available.
• Not waiting for translations as this is not GA'd.

Motivation

• Quality review

Testing

• Manual

Changelog

N/A

[github-actions]

⚠️ Missing Translations
The following strings have been uploaded to Lokalise but are not yet translated.

Manage payment method

If it's okay for these strings to be unlocalized in master (e.g. this is for an unshipped feature), add the label ship without translations to acknowledge that there are missing translations. Otherwise, wait until translations are available in Lokalise and re-run this job.

New strings are localized on a weekly basis and are downloaded as part of the release process. For more details on how to localize a string, you can refer to this link.