Remove `ROUNDABOUT` control context type

[nsenave]

The context "ROUNDABOUT" was added in PR:

• fix: add 'type' property for controls #250

Yet Lunatic only expects "SIMPLE" (that is the default value and can be omitted) and "ROW" contexts.

The "ROUNDABOUT" entry in the enum should be removed.

Two steps:

• mark property as "for removal" in a first release
• remove the property completely in a later release.

[lailabent]

US migrée dans tuleap https://tuleap.insee.fr/plugins/tracker/?aid=10106

[nsenave]

Je re-open pour le suivi côté devs, pour la validation de la TS on pourra se contenter de l'intégration de la version 3.15.3 aux outils Bowie (uniquement Eno Java en l'occurrence).