Update quay.io/keycloak/keycloak Docker tag to v18

This MR contains the following updates:

Package	Type	Update	Change
quay.io/keycloak/keycloak	ironbank-docker	major	17.0.1-legacy -> 18.0.0-legacy
quay.io/keycloak/keycloak		major	17.0.1-legacy -> 18.0.0-legacy
quay.io/keycloak/keycloak	stage	major	17.0.1-legacy -> 18.0.0-legacy

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Release Notes

keycloak/keycloak

v18.0.0

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