jingle-session: remove vestigial GabbleMediaSessionMode enum
jingle-session: remove vestigial GabbleMediaSessionMode enum

noonien-d/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky,freedesktop-unofficial-mirror/wocky,noonien-d/wocky,freedesktop-unofficial-mirror/wocky