keycloak: Enable account console v3 for its custom field support[1]

Our custom Keycloak theme[2] must be updated to use the new account
console[3] which will be handled later.

[1] https://www.keycloak.org/2023/04/keycloak-2110-released#_experimental_account_console_version_3
[2] https://gitlab.archlinux.org/archlinux/keycloak-archlinux-theme
[3] https://gitlab.archlinux.org/archlinux/keycloak-archlinux-theme/-/blob/238889fb36d512f0baa328fad00531ef53c14c1f/lib/src/main/resources/theme/archlinux/account/theme.properties#L1

Fixes: 140b9acd ("tf-stage2: Add an arch specific question for signing up to reduce spam")

roles/keycloak/templates/keycloak.conf.j2

@@ -16,4 +16,4 @@ db-url=jdbc:postgresql://localhost/{{ keycloak_db_name }}
 # https://www.keycloak.org/2022/04/keycloak-1800-released#_openid_connect_logout
 spi-login-protocol-openid-connect-legacy-logout-redirect-uri=true
 
-features=declarative-user-profile
+features=declarative-user-profile,account3