docs(keycloak): update outdated information about revocation_endpoint

[jspizziri]

Description

As of mid-2020, Keycloak has support for revocation keycloak/keycloak#7106. Update the documentation to reflect this.

Steps to verify

Look at the linked PR.

[changeset-bot]

⚠️ No Changeset found

Latest commit: f459040

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[jspizziri]

Just a doc change, nothing else required here.