Google has confirmed that the link to reviews from around the web, labeled "More Reviews," has been removed from the Knowledge Panel in local search results. The feature was present in one form or another for many years and included links to most review sites.
"Reviews from around the web" continue to show in the Google My Business Dashboard although apparently those will also be removed.
Google confirmed the change and made the following comment:
We're always working to make search more useful and experimenting with new ways to present accurate and reliable information our users are looking for. At Google, we regularly make changes to user interfaces of our products based on what content users find most helpful in making local decisions. Going forward, we will continue to evolve the local results' user interface to better serve our users. In order to make sure we are showing the most accurate and current content about your business on Google, links to reviews from other websites will no longer be visible. Google reviews for your business will continue to be visible. Using Google My Business, you will still be able to view and respond to Google reviews.
(Google sign photo via Creative Commons.)