LiveObject: use server gc period for removing tombstoned objects

[sacOO7]

• Reference js PR -> https://github.com/ably/ably-js/pull/2053/files

┆Issue is synchronized with this Jira Task by Unito

[sacOO7]

Reference spec -> ably/specification#350

[sacOO7]

Reference spec -> ably/specification#350

Since some of the spec points are not clear, this will be kept on hold