Bump ejs and oidc-provider in /api

Removes [ejs](https://github.com/mde/ejs). It's no longer used after updating ancestor dependency [oidc-provider](https://github.com/panva/node-oidc-provider). These dependencies need to be updated together.


Removes `ejs`

Updates `oidc-provider` from 5.5.3 to 8.4.6
- [Release notes](https://github.com/panva/node-oidc-provider/releases)
- [Changelog](https://github.com/panva/node-oidc-provider/blob/main/CHANGELOG.md)
- [Commits](panva/node-oidc-provider@v5.5.3...v8.4.6)

---
updated-dependencies:
- dependency-name: ejs
  dependency-type: indirect
- dependency-name: oidc-provider
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>