Small fixes for OIDC client guides

[jedla97]

This fixes #37430 as I go through the guide. Only one thing is not resolved there but in my POV it's better not have it and leave it on the reader.

Also it seems that the default users was maybe changed in dev mode of Keycloak so I update it but the testing part using curl for get token but the guide setting the keycloak address to http://localhost:8180. I would assume this addres is when testing using own keycloak. In that case guide pointing to quickstart ream file which have user admin and alice.

Maybe it would be nice to update the reamls configs in quickstart and quarkus test be aligned with the dev mode. Probably up to discussion but if we want it I can find some time in next two week to do it.

Also the `ProtectedResource`'s is updated because it show in text like `ProtectedResource's . It's probably some edge case in ascii.

[github-actions]

🙈 The PR is closed and the preview is expired.

[quarkus-bot]

Status for workflow Quarkus Documentation CI

This is the status report for running Quarkus Documentation CI on commit ddc0163.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

[sberyozkin]

Thanks @jedla97

[jedla97]

Links to the changed guides https://quarkus-pr-main-43970-preview.surge.sh/version/main/guides/security-openid-connect-client-reference and https://quarkus-pr-main-43970-preview.surge.sh/version/main/guides/security-openid-connect-client

[jedla97]

Also @sberyozkin can you add backport for 3.15 as I doing it when reading RHBQ docs for it