Non-constant time webhook token comparison in Jenkins GitLab Branch Source Plugin

Jenkins GitLab Branch Source Plugin 684.vea_fa_7c1e2fe3 and earlier does not use a constant-time comparison function when checking whether the provided and expected webhook token are equal.

This could potentially allow attackers to use statistical methods to obtain a valid webhook token.

GitLab Branch Source Plugin 688.v5fa_356ee8520 uses a constant-time comparison function when validating the webhook token.