Hide the "Publish Content" button if there are no changes to publish.
When we don't have anything to publish, the Workspaces module still shows the publish content button. See this screen recording for reference.
Problem/Motivation
Steps to reproduce
Enable the Workspaces module.
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Proposed resolution
Only show the "Publish content" button when there is something new to be published.
Remaining tasks
Decide on a message, and styling, to use instead of the "Publish content" button.
User interface changes
Before:
