Fix API performance regression in issues API

What does this MR do?

Fixes a bug where we were continuously generating the HTML for notes and not persisting this to the cache when reading participants.

This MR changes this so that we persist to the cache even when just reading participants.

#218745 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

Availability and Testing

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
Edited by Heinrich Lee Yu