Make MCP_API_VERSION less misleading
Make MCP_API_VERSION less misleading

We didn't release this in 5.15, so it'll be the 5.18 API instead.

freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control,freedesktop-unofficial-mirror/telepathy__telepathy-mission-control