Apicast: use_3scale_oidc_issuer_endpoint of token introspection policy isn't compatible with rh-sso 7.5 or later versions

A vulnerability was found in 3Scale, when used with Keycloak 15 (or RHSSO 7.5.0) and superiors. When the auth_type is use_3scale_oidc_issuer_endpoint, the Token Introspection policy discovers the Token Introspection endpoint from the token_introspection_endpoint field, but the field was removed on RH-SSO 7.5. As a result, the policy doesn't inspect tokens, it determines that all tokens are valid.