Resolve "Remove `pluralize` in favour of `n__`"

What does this MR do?

• Removes the pluralize utility function
• Replaces usages with n__ as specified in our development guide

EE Port

EE Port

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #63553 (closed)