I do believe that prompt is caused because JRE7 is still installed on the machine. It's triggered by the JRE6 autoupdater (because there are no more update for JRE6 and Oracle has coded that response from the web server side of the autoupdater's connection).
Take special note, if you deployed JRE7 using Patch Manager, then JRE6 is not uninstalled by anything. Only if you upgrade JRE6 to JRE7 via the autoupdater is JRE6 specifically uninstalled. You should check the software inventory on your systems for the presence of a JRE6 installation.