Fix Unsharing Workspace

[Sandared]

Describe the bug
When I share a running workspace with a colleague and then stop the sharing he still is able to write to my workspace until he refreshes the window. He is not actively kicked from my workspace as I would have expected

To Reproduce

• Create Workspace
• Share Workspace
• Let other user connect to workspace
• Unshare workspace
• Other user is still able to change content

Expected behavior
I would have the other user expected to be kicked from my workspace. At least he should not be able to change the content any more after I unshared the workspace.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[gtsiolis]

Re-opening as this is still relevant. 📖 Cc @loujaybee @jldec

See also #1125, #1127, and relevant discussion (internal). Cc @akosyakov