Fix revoke access token error handling

[Anderson Valério (andersonvcv)]

• Do not stop flow if revoke fails.
• Properly handle/log error

Motivation and Context

How Has This Been Tested?

Checklist:

• My change requires a change to the documentation or CHANGELOG.
• I have updated the documentation/CHANGELOG accordingly.
• I have created a feature (non-master) branch for my PR.

[Copilot]

Pull Request Overview

This PR fixes the error handling in the revoke access token flow by ensuring that failure to revoke does not disrupt the sign-out process while logging the error appropriately.

• Updated PicsRevokeAcessToken to return only an error instead of both response and error.
• Modified the backendLogout logic to adapt to the changed signature and handle error logging accordingly.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pics_oauthproxy.go	Updated PicsRevokeAcessToken to simplify error handling and response
oauthproxy.go	Updated usage of PicsRevokeAcessToken to match the new error-return behavior

Comments suppressed due to low confidence (1)

pics_oauthproxy.go:38

• The function name 'PicsRevokeAcessToken' appears to have a typo in 'Acess'; consider renaming it to 'PicsRevokeAccessToken' for clarity.

func PicsRevokeAcessToken(backendRevokeURL string, accessToken string, clientID string, clientSecret string) (err error) {