Remove ability to cancel a deployment (for now)

[m--]

We added an attempt to support cancelling deployments in progress, but we need changes on Connect to support it fully. #304 is the issue to fully support this functionality, but in the mean time we should remove what appears to be support for cancellation in Publisher (which doesn't fully work).

Removing this would solve #2179

The functionality to be removed was added within #2071, but we may not want to just roll it back. A simple cherry-picking of changes might be worth considering.

[dotNomad]

Noting here that we still need the ability to dismiss an in-progress deploy, if we still disable the deploy button while something is in progress. This will prevent a regression of #2057

[dotNomad]

We can look into filtering on the stream ID to see if we can ignore the deploy we are "dismissing" to avoid the regression of #2057